Send/Receive SMS on an iPad

I would like to know if one can send and receive text messages on the iPad without having to bother those who are texting you to join IMs etc.

Google voice is a good option. It lets you send and receive texts from anywhere you have Internet. You get a phone number through it.
It's completely free, and you can use Google's iPhone app on your iPad. Or, you can buy GV Connect for iPad.

Skype for iPad?

But to receive the messages you have to configure your Skype account with your mobile phone number and then you will receive the replies on it instead of the iPad.

Also, give Textfree a look.

iMessage in iOS5 will bring about some of this, but only for other people running an iOS5 device. Viber and other similar apps to the same thing but they're even more niche.