I feel like their homepage design gets copied pretty often. Perhaps they're on to something?

If you're curious, for our marketing site, we took inspiration from a couple of different sites, including 37signals, chartbeat.com, goodbarry.com, freshbooks.com and a few others I can't remember off the top of my head. I bet a lot of the aforementioned sites took some inspiration from 37signals as well :).

For the application site, we started with the open-source Web App Theme (http://github.com/pilu/web-app-theme/tree/master) and changed it to suit our needs.

actually, i take that back - it did immediately remind me of a previous homepage design of theirs...not the current one though

It looks very similar to the Basecamp and Campfire designs (ex: http://campfirenow.com/). However, both of those designs are fantastic, and I don't see too much of a problem with using them as design inspiration for a non-competitive company.

It looks like peashootapp.com which looked like basecamphq.com...

http://peashootapp.com/

wow, it does not look like peashoot. It is a near-exact clone of the site! I'll leave my personal opinion of the matter at the door..just saying!

I thought the exact same thing actually.