My own "Muddle Puddle" received its first review on itunes yesterday (apparently it is frowned on to put a link here so if anyone fancies taking a look you'll have to go via my profile). "So what," I hear the cry. The point is I know it seems to be the accepted practice to stack reviews up by paying for them but that idea makes me uncomfortable so I've drifted to just letting it happen naturally.
There's a thread on the notice board that's all about us helping each other out. I've reviewed works by three authors already and am about to start reading another one this weekend.
If you're willing to give back by doing a few reviews yourself and are willing to give and accept honest opinions on your work, that may be a good option for you.