I know if I send one to an Alltel number I have to use
but teleflip should work for most carriers. I have used this and it doesn't bill as an outgoing text, it is included in the data plan.
I haven't tried it personally but I think that people with regular phones can send text messages to an email address, at least someone told me they could. So you might be able to get around incoming text messaging if they send it to your blackberry email address, good luck trying to make that happen though.