Probably the best app for texting is Handcent SMS which gives you the option to select multiple recipients.
Chomp SMS is supposed to be very good also, tho I don't have personal experience.
The other alternative is an app called MeContacts which gives you a screen of tiles (4x3, 4x4 or 4x5 from memory) that you allocate to one of your contacts and you can add numerous screens so one for friends, family, work etc whatever you choose. This app then gives you the option to select multiple recipients too for sms.
