Wether or not you need extra qualifications aside from your degree (if you have one) is a bit tricky to define. I think a lot of people would like to know wether this is a worthwhile endeavour seeing as they are often not free and can actually be quite expensive depending on what it is and who it is run by so I am going to try and explain my current view point on the external Qualifications thing. First of all what exactly are we talking about here? There are all kinds of qualifications that you can sign up for and some are based purely in software others are based in specific design practices like email
design and SEO etc.
1. The "Adobe Suite" training certificates are probably the most widely recognised qualifications for software largely because the Adobe Suite has become an industry standard software package across design professions. They range in difficulty from the "Certified Associate (ACA)" level to the "Adobe Certified Expert (ACE)" level and the finally you can become an "Adobe Certified Instructor(ACI)". All these courses are listed here with a much more detailed explanation of what they entail; http://www.adobe.com/support/certification/ You can do certain packages individually or you can go about completing the training for an entire suite in one go, and that will of course affect the pricing but can be more productive and cheaper than doing them one by one. These will to be honest help your CV to stand out from the crowd because every single designer suggests that they are great with every single software but few of them are certified by Adobe and can prove it!
2. Lynda.com is gaining popularity from employers all the time as it offers various courses for all kinds of software in a monthly or yearly subscription plan. This is something that you can go back to time and time again and keep up to date with all the current technologies and trends so is fantastic as a training tool. As far as qualifications go this is as good as any and you can have a certificate of completion for every course that you go through. http://www.lynda.com/home/Player.aspx?lpk4=80569&playChapter=False There really isn't any software left out of the data base and the teaching style gets great reviews from student and teachers alike.
1. The "W3C" or the "World Wide Web Consortium", have a website from which you can learn standardised coding for the web. These are in fact free lessons that you can get at http://www.w3schools.com and then you can get certified for around 60 pounds per language you take. I actually have one of these myself and I have to say that they definitely help you to stand out. You are probably being hired by an HR department rather than a designer at least in the initial stages so it will help you to get your foot into the building at least. The rest of course is up to you. It is probably worth mentioning though at this point that you can only learn web related languages and scripts from this site and not software programming languages like C or Java. These are for programmers rather than designers and will most probably be useless to you as a designer.
2. There are numerous "CIW" (Certified Internet Web professionals) accredited courses that you can do in web development which were invented by a community of web designers and developers during the dot com boom and have survived to this day. These certificates are not easy to obtain and they are not cheap either at around 600 pounds a course. However they are internationally recognised and they do teach job specific skills rather than just vague principles so definitely worth taking a look at. They remain popular with many employers because a large number of university teach them across the UK, Europe, and US.
There are numerous courses that teach general design practice and in fairness wont do you much better than having a degree. This is a pre requisite of most job adverts these days so if you are going to study a broader topic then personally I would advise that you do it in a degree and at least have that piece of paper to get you into the interview room. Im not saying that these kinds of certifications are worthless by any means because they will probably teach you the things that you were too hungover to hear about in your lectures but from an employers perspective there is too little known about the worthiness of such a course and they don't want to have to do the research. If its accolades are easily "googleable" then by all means go for it, but if nobody has taken it or heard of it then I would steer well clear and keep your pennies in your own pocket.
Long term advantages.
It would be nice to think that you could go to school and be done with it and then just walk into a job but unfortunately that is not the way the world works. There isn't just one glass ceiling either there are many! If you think about it in the world of work and most especially graphic design there are pay brackets to consider. when you are in an entry level role you can expect to earn around 14-18k per annum, then when you are in a junior role you can expect to earn between 18-21k per annum, now there is a little more scope in a mid-weight position depending on the company that you work for so you can expect to get anywhere between 21-30k per annum. Senior roles 28k plus and so on. How much of that depends on external qualifications and outside factors is really not that easy to judge but I do know that if I were presented with someone who hadn't done a days education since school (on paper at least) and someone who had actively seeked out professional development certificates and courses throughout there career, I would likely choose them for the promotion. Not because it means that they are better than those without the qualification, but because it says that they are willing to work on there mistakes and grow as much as they can. Businesses need that. (at least in my amateur entrepreneurial brain they do anyway).
Short term advantages.
I have found actually that since having taken a certificate or two and this may well just be co-incidence, that I have been getting a lot more interested parties for freelance work and a lot more interviews for jobs. I haven't actually secured any of these jobs so I cannot say that the certificates have helped me in so much as actually getting me into the company but they have got me a damn site nearer to the building and that is an achievement it today's economy I can tell you (I probably don't need to I'm sure you already know). So i have decided therefore given the long and the short term benefits from a little upfront cash, that getting external qualifications will indeed help you and they will help you with the big players like agencies and such because they care about achieving. they care that you are a winner just like them so you might as well get cracking.
It means more studying! It also means more money and of course the time investment on top of that. Often you will have to work these kinds of courses into or around your working day and so can make your life a little bit more stressful in the short term. You will have to do the research yourself into whether the course you choose is worth this kind of investment which is again more work on your behalf. They are also not a guaranteed fix and trends with courses are much the same as with technologies. What was once the hottest thing since sliced bread can quickly become yesterdays news so you will also need to figure out the kind of longevity that any given certificate holds.
Overall though I think they work more in your favour than they do against you so if you are trying to jockey your way up the career ladder then professional development certificates will certainly help you in your quest to do so within your specified field.