The list of printers that support AirPrint wireless printing from the iPad is growing, rapidly. When I last posted about the supported printers list back in June there were a total of 217 printers from 6 manufacturers. Today there are over 430 supported printers from 13 manufacturers.
Here’s a little more detail on which printers from which vendors work with AirPrint:
Brother: 63 printers from the DCP, HL, M, MFC lines.
Canon: 95 printers from the IP, MG, MX, and Canon Pro lines.
Dell: 4 printers from their B and V lines (eg B1260dn and V725w)
Epson: 92 printers from lines including Artisan, EP, PX, Stylus, Workforce, WP, and XP lines.
Gestetner: 11 printers from their DSc and MP lines.
Hewlett Packard: 57 printers from their Deskjet, Envy, Laserjet, OfficeJet, and Photosmart lines.
Infotec: 8 printers from the MP line.
Lanier: 8 printers from their MP line
* Side note – maybe some fresh blood needed in the printer naming arena?
Lenovo: 3 printers from their LJ line
Lexmark: 47 printers from their C, E, X, OfficeEdge, and Lexmark Pro lines.
RICOH: 16 printers from their Aficio and Imagio lines.
Samsung: 20 from their CLP, CLX, CPL, ML, and SCX lines
Savin: 8 printers from their MP line.
You can see the full list and make sure a printer you own or plan to buy is on it at this Apple support page
There are a good number of AirPrint printers available to be purchased in the Apple online store, starting at around $100.

Can I connect my existing printer (HP office jet model 6210 all in one) directly to my wireless router with an ethernet cable so that i can print from my ipad? I read this somewhere as I was shopping for an air printer.
I gave up on AirPrint enable printers a while ago. I just wasn’t in the market for a new printer. But then I discovered the Printopia app for Mac – which has really solved the problem for me. I can now print from my iPhone or iPad on my own wireless network as long as my Mac is on and awake.
I agree with neena, i had a good working printer in jan last year so why spend more money on airprint enabled one
personally when it comes to apps i am more of a fan of Print n share tho ;)