http://www.dd-wrt.com/phpBB2/viewtopic.php?t=172030&highlight=wnr2000
Looks like flashing the WNR could be a bit of a chore.
If you're talking about the wrt54g, the link depends on the specific model.
http://www.dd-wrt.com/site/support/router-database
Router database for DDWRT shoWs support for the WNR-2000 v3.
You can get WRT54G's on eBay all day long for $20 bucks or less. Just check the model # first.
Even the Micro build of DD-Wrt supports Wireless Mac clone.