Not sure what you mean by "no strings," but if you mean free money without any hand requirements, then I second the Royal Vegas nomination.
If you are just looking for a "no deposit" free money offer, but are ok with having to play some raked hands before cashing out, I would suggest
http://www.instantbankroll.com. You can get $75 free at Party (plus a $25 bonus once the raked hands are complete) or $50 free at Titan (plus a $25 bonus). New accounts only, of course.