Yeah, if there's a Mac in the mix you have to make sure the gadget will play nice. The Brother printer I mention seems to play nice with both; I only have Macs in the house.

I forgot to mention another option could be a different wireless router that has a built-in print server function. The print server on these is usually wired for USB, though, so you still need the printer to be near the router.

If you do have an HP LaserJet then yes there are network cards that can be plugged in, although you may or may not get them any cheaper than some other solutions.