I have to second this. I do not have an eye for design and I know this. It's just my weakness. Having a good designer on board is an absolute must. If you want a suggestion, try http://www.monfx.com/ | http://www.mdolon.com/ -- he is here on Hacker News and he designed http://www.feedbackarmy.com and http://www.afterthedeadline.com for me.