Seesmic

Seesmic for iPhone lets you update and view multiple social networks in an efficient and powerful application. Manage multiple Twitter accounts, your Facebook account, a Ping.fm account and organize all your accounts, searches, trending topics and lists in your customizable dashboard.

Features include:
Seamlessly manage multiple Twitter accounts
Explore and save Twitter Searches and Trending Topics
Browse Twitter Lists, share your location by Geotagging your updates
Facebook support
Ping.fm support that lets you update dozens of social networks at the same time (including MySpace, Wordpress, Tumblr, LinkedIn, Flickr, Blogger, and many more!)
Store updates into Evernote
Post to multiple accounts at the same time
Share photos to the photo sharing service of your choice
Tons of other great features!