Built an app for tweeters. Nothing great to look at, and it doesn't tweet to be specific. In fact I just built it for viewing it from my phone web browser.
You've two options when tweeting. Do it from the main web page (i.e. the standard version) you have a list or trends in the sidebar. You can catch the current vibe on twitter (real-time!). On the light-weight mobile web version you can only view tweets that would appear on your profile, no trends!
So even though my phone can browse to the standard page, it is heavy, and you'd have to scroll a lot to get to the trending topics part. I've designed a page that just returns the trending topics only. (Notice the url in the title of this post)
Now when you are with your phone, and you feel like tweeting, and you don't have something to tweet about, you know where to find what is the most tweeted on twitter.