SocialScope doesn't have myspace, which is a downer. Also it doesn't integrate with your messages folder for replies etc. So I still keep facebook and twitter installed for those reasons. But if you just want it for posting to these services you can set your twitter to post to facebook and myspace.
I use foursquare, in it you can just "shout" something to FB and Twitter. The Check In at places is also fun to do. I don't have myspace, so not sure if it works for that as well.