I like handcent.... its neat and clean and give you options to customize for your liking. Ohh and its free on the android market. My only complaint is that my phone receives texts and flashes that little "quick message" and does not automatically open handcent for the texts... so if you ust read and respond to the quick message Handcent still thinks there are texts in your inbox that you have not read. Hadncent also gives you the little smiley emoticons with actual picture not the symbol
Minor issue for me.
There is also WhatsApp but you and your buddy have to have the app downloaded to use it.