For whatever reason, none of the multi-protocol services, like Astra/Trillian, Seesmic, HelloTxt, etc., allow you to simultaneously post to multiple Facebook accounts. (I am, of course, ignoring the fact that FB doesn’t even want you to have multiple accounts.) I did a little research and people have come up with a variety of different solutions, but I think I’ve come up with a simple and elegant way to do it.
My current fav of the multi-protocol bunch is HelloTxt. I like the way you can group a set of networks together to post to, or pick a set based on tags. It supports more social networks than you can shake a stick at. It has a nice mobile version, as well as the ability to post via email, IM, text message and more. Note that to use text messaging you need an international plan, so US users should generally stay away from that feature.
HelloTxt lets you add more than one Twitter account, but only one FB account. I think it has something to do with the way to have to install the HelloTxt app on your FB account. For the most part, the other networks just require that HelloTxt knows the login and you can post.
First, you need to set up a Twitter account that you only use when you want to post something to your second FB account. Use a Twitter name that starts with facebook, so it’s easy to recognize. On the Twitter Account Settings tab, enable the Protect My Tweets option. This keeps all your posts private as far as Twitter is concerned.
Go to FB and log into your second FB account. Add the Twitter application to FB and allow it to update your FB status from the FB-Twitter account you just set up.
Go to HelloTxt and set up your first FB account normally. Add the special FB-Twitter account to HelloTxt as a Twitter account.
When you are done, you can simultaneously post to both FB accounts from HelloTxt. In theory, you could use this method to post to more than two FB accounts. Unfortunately, you can only monitor the first FB account. I’m still hoping that either HelloTxt or Seesmic implement native support for multiple FB accounts, but perhaps there is some sort of developer TOS that is precluding this.
UPDATE 2010-08-01: See my new way to do this using Pixelpipe.com