As jbcohen mentioned, some Borders stores are closing, you can find out if any of those near you are on the list by using the store locator at Borders.com. There is also a list of closing stores here
http://s.wsj.net/public/resources/do..._20110216.html At the stores that are closing, people have been finding Kobos for $79. See this thread
https://www.mobileread.com/forums/sho...d.php?t=123770 Whatever other readers they have still in stock are likely to be 20% off as well, I think they carry Sonys and Velocity Cruz, and they used to have one of the black and white lcd readers but I don't see that on their website now.
Barnes and Noble has been selling refurbished wi-fi nooks for $99 on ebay,
http://cgi.ebay.com/Barnes-%26-Noble...68660.m2000036 which is a pretty good price.
Other than those I haven't seen any good sub-$100 deals.