Is there any way to activate an instant messaging prog on the 7100T without additional cost? I figure there must be a way, and someone here must know it.

And, by the way, I've heard of BlackChat, but is it safe? I'm a newb to the whole PDA game and was wondering how I should go about getting a free IM prog.

T-Mobile has a free one, but it uses SMS messages, so unless you have unlimited SMS on your account, it can get pricey.

There's always RAMBLE IM for AOL instant messaging. It's free

Is Ramble safe? Do I have to worry about it messing up my 7100T?

Wirelessly posted (7100t: BlackBerry7100/4.0.2 Profile/MIDP-2.0 Configuration/CLDC-1.1)

Yes. It's safe. I've used it on my 7100t without any trouble.

And T-Mobile won't charge me for IMs sent? I don't have Instant Messaging built into my plan. This seems impossible. Is it billed as an SMS message, then?

Yeah, it uses a data connection. The app has an option to use a wap connection or a BES connection. Either way, it doesn't require use of sms

My 7100t (T-Mobile) came with three programs. Two of them had problems.

AIM: Couldn't populate the buddy list, because I guess that's some kind of bot that can't be loaded. I can add manually, but that's a pain.

ICQ: It said my number or password were incorrect. I check them a few times and even logged in on my computer. It won't recognize the number.

YAHOO: This one works perfectly. I have my entire list and haven't had any problems with it yet.

I concur with Redtruk's recommendation of Ramble IM. You can find it here"
http://wireless.sra.com/ramble/
I've been using it for a while now and no issues billing or otherwise.