Can you use goggle add sense on pages like your myspace page ?

What about a Yahoo chat group or forum ?

You can use adsense on any site that allows the code to be posted, BUT you may fall fowl of the site's own T&C.

But on web sites that I own, as long as I don't mind their adds, I can use it ?

Yes indeedy.
Adsense tells you how to put the code in: https://www.google.com/adsense/login/en_US/

Yep, I've been meaning to put it on my site, but have been too lazy.

Ok, added it to my one web site ( maybe) most of you know the pain I had getting it set up before.