There are better ways to find logos that things like 99 Designs (as much as I am a fan of a lot of SitePoint's efforts in our industry I am not so sure about 99 Designs). If you really need a pre-fab logo -
Pixel Logo is pretty good.
Having said that, I much prefer using local designers to do my graphic design work, and have a couple of designers I work with. If you would like more information, PM me and I can send you their contact details...