PublishThis.com: a WordPress plugin with its own index. You can input sources if they aren't included already.
ScribbleLive.com: use for live event coverage. Embed code to include it on your blog. You can include content from Twitter using @names and #hashtags so that it's participatory coverage of an event. This gets you the network effect.
Storify.com: you search on the platform for your topic of whatever story you want, you can order posts for flow of information. You embed it on your site. The most potential here is if some story is actually breaking or unfolding via Twitter.
RebelMouse.com: here's an option to have a "blog" presence on your site that's actually pulling from your social channels. If you "power" a page through RebelMouse, you're getting the on-site traffic, potentially habit building, giving a central location. I really like this option for "personality" brands like Gary Vaynerchuk.