Handcent is a text messenger for android and I use it over the default text message application. Handcent allows you to send and save SMS / MMS. It also allows you to search, comes with a quick popup / reply box which I love.
Easily attach sounds, music, audio files, backgrounds, videos, pictures and camera pics with a couple quick taps. I wouldn’t use anything else. Also comes with threaded view and iPhone layout look along with a few other themes.