I got in a whirl about Twhirl the other day because it let me post to multiple microblogging services at once. Today I've been checking out a service called Ping.fm which ups the ante by letting you blanket Twitter, Jaiku, Pownce, Tumblr, and Facebook with the same short form message.
All you need to do is link up each account (it only works with one from each) and send said 140 character message to a special e-mail address provided by Ping.fm. Your message will be sent to all the networks by default, but there are also small shortcut codes called "triggers" that will let you choose to only send your message to that specific service.
In addition to e-mail there's an instant-messenger bot that works with AOL. I'm also hoping to see a short code that will make it as easy to post to via SMS as Twitter is since some phones don't let you send SMS to an e-mail address.
I do worry sometimes about the idea of blasting out the same message to several services at once. As I've said before, each community brings with it different levels of interaction, and distancing yourself from that means you're likely to miss other people's replies. Mixing something like this up with a service like SocialThing or FriendFeed could be a solution, but let's not forget about core services we're using in the first place.
Ping.fm is currently in private beta although if you use the invite code "Webware" on this signup page you'll get in.
Update: Webware reader Molzymcd notes hooking up your Twitter account (and potentially others) sends out a one-time message that advertises that you're using the service. If you're not okay with this, don't sign up. Better yet--let the creators know.
Update 2: Alright, we've rounded out some more updates. There are 250 of these, so get em while they're hot. Just enter "Webware" as the invite code.