You've got the 'who' nailed, but it sounds like you're not completely satisfied with the 'what' and don't have anything about 'how'.
How about something like ...
"Talentopoly helps programmers, designers, and IT professionals stay at the cutting edge of their professions by ..."
- "Learn from the most talented programmers, designers, and IT professionals today"
- "Discover and share the best resources to make you a better programmer and designer"
Make your mission clear, and separate from your methods. Then if your methods grow and change over time, no one will be shocked.
It's fairly vague, but I think if done the correct way, vague excites people to check something out.
Personally, I particularly like the concept of Kaizen (continuous improvement) when reading this post- this seems like essentially what your company is allowing people to do for their knowledge/brain. You could go for the whole stay competitive/stay ahead of the competition/professional-personal development deal, but eh. When everyone says the same thing it sorta loses its appeal.
I'd been toying with a somewhat similar idea in the past and wish you the best of luck with it. Knowledge transfer should be one of the most important industries in the future. When I was looking into it I'd found some that offer a similar idea, but for professors to post research articles about the areas they're interested in. The name escapes me, but if you poke around and are able to find them that may give you some ideas as well.
These are all more tagline type things, but maybe they'll spark some ideas: 'User generated Kaizen for your brain' 'Community created continuous knowledge improvement' 'User generated continuous skill improvement' 'Professionally generated Kaizen for your brain' 'A professional community designed to allow you to continuously improve your (programming/designing?) knowledge /skills'