Social-networks crossposting question

Does anyone know how to crosspost to (or from) Tumblr, Facebook, LiveJournal, Twitter, and Dreamwidth to (or from) the others? It's tedious and time-consuming to manually do so, and I usually forget to include one or many when posting about something that might be relevant across platforms. Also, the LJ world has gotten very thin, so it would be great to make sure more than a handful of people see things.

I also want to be in control of what gets crossposted and what doesn't.

I _do_ know how to crosspost between LiveJournal and Dreamwidth, but the others are a cypher. Ideas?

Thanks!
Chris