If you are anything like me you know nothing about creating a theme and are never satisfied with the standard ones.
I don’t know about ‘professional web 2.0’ but this place has a few good ones.
I use one I found here
Just for the record, check this post: http://www.fluther.com/disc/2404/where-can-i-get-tumblr-themes/
Honestly though, at the end of the day the best ones are all custom. Know anyone that could write one up for you? (I suppose if you did you wouldn’t be asking this question…)