I almost joined the 2009 edition of the Decades Challenge, but talked myself out of it at the last minute. So this year, I'm giving in and joining up.
The challenge runs throughout 2010 and is being hosted by Michelle from 1MoreChapter. You can read all about it and sign up by visiting the challenge announcement page, but the basic idea is to read a minimum of ten books in 2010, which were published in ten consecutive decades (books published since 2000 don't count). Crossovers with other challenges are allowed, and your list can change at any time.
The challenge announcement page has links to lists of eligible books, in case you need some suggestions. I'm thinking of reading the 20th Century, 1900s-1990s. Haven't decided on any titles yet, but I'll be updating my progress on my challenge blog.