paper.li - Read Twitter as a newspaper based on your own profile and who you are following or based on lists or hashtags.

Twitterfall - See tweets for specific lists, searches or trends

Twazzup - Really nice tool where you can see not only the tweets for each keyword but also images and key influencers.

Trendsmap - Real time local Twitter trends. “Pumpkin” is a really popular term in California right now :)

Listorious - find people to follow based on tags or lists.

Twitterdesigner - Easy tool for designing your own background.