http://www.tonywright.com/2007/bootstrap-design-for-geek-pow...
That's for tight budgets only-- if you've got a budget, find a usability/UI god and pay what they are worth. :-)
If you're looking for "cheap" work, you could visit FreelanceSwitch.com and post on their job board or get involved in their forum and try to find someone that way. Also SitePoint.com allows you to hold contests to pick the best work, though most good graphic designers stay away from the contests because it is considered unprofessional to submit work on spec.
They are all "leaders" in design, many have written books that are widely available in bookstores, etc.
You can look at their portfolios and get a sense of the broad range of products / services they have completed designs for.
http://contests.sitepoint.com/contests/3313/entries/200711.j... http://contests.sitepoint.com/contests/4358/entries/272610.j... http://contests.sitepoint.com/contests/2241/entries/130440.j... http://contests.sitepoint.com/contests/2275/entries/132753.p...
Each of these designs cost between US$350-$700.
You can judge the quality for yourself... in our opinion they're excellent for the price.
However, the contest process is time consuming and it does take a bit of practice to understand how it all works and manage your contest in a way that delivers the best possible result.
a super nice chick - fun to work with - and hella responsive. and SF too.