It depends what sort of site you've got really. A lot of people make a site, generate some traffic by writing lots of quality content and swapping links, plonk AdSense on it and then sit and wait. It's a shrewd idea to try a few different monetisation methods to maximise your earnings. If you're trying to monetise an existing site with PR you could do a lot worse than trying Text Link Ads who pay pretty generously and by PayPal - check
this review for the full low down.