Sadly, a few fine Apps are banned from the official Market by Google (e.g. Transdroid): How can I keep those Apps up to date, without visiting the project sites regularly?
Try using aTrackdog, pretty sure that'll be what you're looking for!
I usually sign up for an RSS feed on the project's website, and add the feed to a separate group in Google Reader. Since I sync up with Reader twice a day, when an update to an app I'm following is available I know about it the same day.