Two of my all time favorite Mac OS X applications just came out with new releases:
Adium Xis a beautiful multi-IM-service client. It's based on GAIM but with a true OS X user interface. For PC users, it's kind of like Trillian but nicer! They just came out with a new version. The one thing everyone hasn't done yet is to add Skype IM support. They are coming on strong as a competitive IM network.
Ecto is a beautiful multi-blog-service authoring tool, in other words, it gives you a nice and rich edior for your posts. They also have just come out with a new release. For me the key new feature is Technorati Tags support.