What is the best site for free advertising?

I need some free, but effective advertising for my sites but I can't find any. Who knows a good site for it?

I've had the best luck with easy to use and free advertising site http://104inc.com. I listed with them a few months ago for a free account and I get leads from they daily. From all the free advertising sites I've tried, this is the only company that gives me qualified sales leads from local/national and international customers. Good Luck!