I'm planning on upgrading my home network from 100base to 1000base, the only device in my network without a gigabit network card is the printer.
What are my options?
Is there some kind of converter I could use?
If the switch/router you're using supports both 100 and 1000base (which it likely will) then it should be fine to connect every device to it at 1000base.
The only communication in this case that will be slower will be from the switch/router to the printer (100base) everything else will go at gigabit speeds even while you're printing.
This has been the case for me with my Netgear and D-Link equipment, other brands or cheaper models may react differently.
Only other option - without buying a second router and creating two mini networks - would likely be buying a newer printer (they are pretty cheap now anyway).
Find out a little bit more about the transition here: http://www.windowsnetworking.com/articles_tutorials/Transition-Gigabit-Ethernet.html