Text links.

If PPC isn't working out for you, sell text links! It's a good way to get that revenue you're lacking.
The higher your PR, the better your traffic- the more links on your site are worth.
I've made pennies from PPC programs but I've made thousands from selling text links.
My highest PR reached on any and all of my sites was 3.
If I can make thousands from a few low PR sites, imagine how much you could make from yours!
If you're not sure how much to sell your links for, search around a bit. See how much other people are selling their links for and what their traffic and PR is like.
Remember though, YOUR links are worth how much YOU can sell them for.
If you feel like you can sell it for double the amount other people are selling theirs, do it!
There's some serious money to be had.