Most wordpress themes work fine with bbpress. There are plugins such as https://en-gb.wordpress.org/plugins/bbp-toolkit/ and https://wordpress.org/plugins/bbp-style-pack/ that will help integration and add features
There are a few WordPress themes that you can use.
WP Knowledge Base
There are also other free themes that add functionality for bbPress here and there.
And there are a few good premium themes on themeforest.
@heero I know this thread is old but it still shows up 1st page when I search bbPress themes. So I thought it would be worth providing an upto date answer for future viewers.
The 1st stop I would recommend is checking out wordpress.org/themes where you can find thousands of themes.
However, if you don’t want to spend all day looking through their directory then check out Softwarefindr a platform were forum owners using bbPress give a shortlist of their recommended bbPress themes.
According to me “Responsive Theme” is the best theme for any forum based site, there are so many very useful SEO friendly options which normally other popular themes do not have.
One of them is Last updated date…and special bbpress theme layouts
You can also try Magazine Pro by StudioPress. It’s a bbPress ready WordPres theme with a very professional look and a lot of features.
Magazine Pro Theme