Blood, the journal of the American Society of Hematology (ASH), provides access to a collection of Free Research Articles. There are currently 551 articles (published between December 15, 2008 and May 1, 2004) in the collection.
The most recent article in the collection, at present, is one of the ASH 50th Anniversary Reviews: Stem cell concepts renew cancer research by John E Dick, Blood 2008(Dec 15); 112(13): 4793-4807.
Added December 15, 2008: See also the Public Access policy of ASH.
Be openly accessible or be obscure 