Google has rolled out a new algorithm update.
My advice would be - DO NOT PANIC!
Don't start spamming your sites with links, web 2.0s or anything of suck kind. Wait it out. Your website will come back. One more thing, the panda update stated clearly that if even 1 page on your website is of low value (duplicate content, too little content etc) then it WILL decrease the rankings of all the pages in the SERPs.
So, instead of getting backlinks, improve your website and add MORE original content to it. You will be back!