Smart move and quick fix for now. Definitely look forward to an ability to connect wi-fi to a printer and print to it. Expect apple to be the first to make one of the lexmark printers "iPhone capable" when filesharing becomes more prominent on the phone.I found this on the net.
1. Create an AppleScript on your home computer which prints the attachment from any email which has 'PrintLW640' (or whatever you like) in its subject.
2. Open Mail on your iPhone/touch, add 'PrintLW640' (or whatever name you want to give it) to the subject (like 'NewProspects PrintLW640'. Send the e-mail to your home email address. The attachment will automagically be printed...
3. More than one printer? Add multiple scripts with different printernames (like my PrintLBP5000 for color prints ;-).