You could always try http://typecast.com for this, which allows you to preview and compare fonts from multiple web font providers (disclosure: I'm on the team there).
Haha, I actually thought of Typecast when I loaded up this site! (I'm from Belfast, not too many apps of that quality around here! :) )
A little ashamed to say that I haven't used it yet (I'm a developer more than a designer, so just haven't had the reason to try it out properly yet. I guess you shouldn't really need a reason to experiment though!), but it looks gorgeous and a really useful tool to have.
A little ashamed to say that I haven't used it yet (I'm a developer more than a designer, so just haven't had the reason to try it out properly yet. I guess you shouldn't really need a reason to experiment though!), but it looks gorgeous and a really useful tool to have.