When searching, you can search for just the free apps. And there's plenty of them. And many of the ones you do have to pay for have free "lite" versions, so you can see if you'd like the full version.
I've only bought one app and that was the full Weather Widget app. They do have a lite version, but I wanted the full one, which is customizable. That one cost $1.59, if memory serves me.
You can also check for the newest available apps, and there's constantly new ones. I think it's safe to say we'll have plenty to keep us entertained for quite some time.