Well for texting I would get one that will work with your friends texting software.
For com stuff, you can turn your iPod into a phone (free calls) as long as you have wifi & an earbuds with a built in mic (about $40), I have not seen over the ear headphones with mics
Skype, Skype to Skype call is free but I think there a small charge if you call a none Skype number but not 100% sure.
iCall, 100% free that I know
Fring, 100% free that I know....
Otherthings must have...
Bump, Bluetooth
PhotoShare, Bluetooth
Mover, Bluetooth
it is good to have more then one incase the other person does not have XXX software installed.
I just received a 2nd gen ipod touch 8gb and I would like to use a free text messaging app on it just for fun. What is the best app to use? All suggestions would be greatly appreciated.
Any other cool communication app suggestions are also very welcome! Thanks!

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic