I always list freelancing on my resume. Always have. I'd look, well, dead today career-wise without it.
For the sake of clarity, I merely list notable clients I've worked with as a freelancer. In addition I'm a firm believer any resume should be one page. I don't care how great you feel something is, all content should be displayed on a single page.
Freelance 2001 - present
- Client A 2001 - 2012
- Client B 2002 - 1003
- Client C 2003-present
- Client D 2004-2006
I don't go into listing specific job duties much at all on my resume. The goals is to get a call back. To this end, I'm fine with leaving a little mystery. It may actually be helpful if the person reviewing the resume wonders what you did for "Client C in 2005". I never go into company size, department size, or anything remotely specific. Honestly, I don't think they really care, and if they do... I get a call back. Remember, you're not trying to educate anyone on the companies or clients you've worked with. The resume is a chronological account of your employment, education, and skills.
The problem with listing the work you did while freelancing is that it can build expectations. If you put down that you designed a series of illustration for Client A in 2011, and you do not include those illustrations in your portfolio, you may be putting your foot in your mouth so to speak. Keep the resume straight-forward and general in my opinion. Allow the portfolio to speak about your abilities.
I, personally don't ever list any "duties" or "responsibilities" on my resume, never have. If I feel I posses some notable skills or abilities, I list then under skills and abilities, where they will be seen. As opposed to buried under some employer listing as "duties". People do not want to read a resume. They what to skim it and gain quick insight.
The overall list of employment + freelancing reflects my time in the industry and the freelancing reflects my ability to work with clients.
Realize that many will simply include a line that reads something like "Freelance 2010 to present" and nothing more. That is not helpful. In many cases, for designers, it's kind of understood you're doing things "on the side" which could be called freelance. By listing clients, you provide direct connection to the work. Avoid the random "freelance" line unless you're going to list at least some specifics such as client names.
If you want to go one step further, adding contact information is a good thing as well:
Freelance 2001 - present
- Client A 2001 - 2012 : Bob Jones email@example.com
- Client B 2002 - 1003 : Dave Smith firstname.lastname@example.org
- Client C 2003-present : Jane Johnson email@example.com
- Client D 2004-2006 : El Conquistador Robinson firstname.lastname@example.org
This allows the potential employer to contact the freelance clients. Be certain to ask the clients if this is okay first.
What you can do, your abilities, your design aesthetic, are all things for your portfolio not your resume. Reserve explaining what you did for Client A for your portfolio when showing off the work that's the point of the portfolio, not the resume.