How to keep articles organized - sorting papers (Aug/12/2009 )

It may sound retarded but have a look at itunes... i noticed you can import pdf files as ebooks, you get a nice thumbnail of the cover etc.. works ok and it is free

You can also use Endnote for this. But there you have to be carful not to exceed the 60 Mb per month, otherwise you might have to pay for a pro account.
For me "Zotero" - the Firefox add-on - works best!

I get EndNote free through my school, but just downloaded Zotero to check it out, definitely looks great so far!