MessageCast announced that its LiveMessage Blogger alert service has gotten 10,000 subscribers in its first week. Some cool blogs such as Bink.nu are using it.
To see how it works, you need to have Microsoft Messenger running on your computer. Go to a site running LiveMessage and click on the appropriate link (e.g. Bink.nu has a LiveMessage button, Flexbeta has a Flexbeta Alerts button, Feld Thoughts has a LiveMessage button, and OnlyOnce has a LiveMessage button.)
If you have a blog consider trying out the LiveMessage Blogger alert service as an option for your blog subscribers.