Twitzap is a web interface for Twitter that works like an application. It automatically refreshes your twitter stream and any channels (basically, saved searches) you subscribe to, and keeps track of how many unread messages you have in each channel. It's also got a lot of other neat little improvements over the standard web interface, some of which Twitter should probably look into adopting for itself.

Channels are the main perk of Twitzap, and it treats your @replies and direct messages as channels, too, combining your incoming and outgoing DMs into one neat list. You can also quickly add trending topics to your channels from right in the sidebar. Other features including chatting over Twitzap with other users who are logged in and a retweet button for each tweet, next to favorite and reply.

The overall interface of Twitzap looks a lot like regular Twitter -- it even uses your Twitter background when you log in -- so it should be very easy to get the hang of using. I'll be honest: I expected to be writing an "oh god, not another Twitter client" review here, but Twitzap really does have some good ideas.