Well, for the complete list of printers that you can print to wirelessly, see the "Printer and Scanner Software" link in this "Mac 101: Printing" article.
I've attached the entire article because it describes the simple setup process if you have one of the supported printers.
All I need is something VERY SIMPLE. Don't need copying or scanning or faxing. Just printing, and not even color printing!!
Consider one of these:
I know you want something simple so you don't need AirPrint, but an AirPrint compatible printer is not much more expensive than one that is not.
You will be able to find of the laser printers above for less than $100 and you may never have to buy a toner cartridge for it.
I saw this one at a Wal-Mart recently for $100:
Not AirPrint though...
Cheapest yet, but not wireless, USB only: