I have about 109MB free total according to System Settings, but only about 31.18MB free in the System. I cleared the cache from every single application, formatted the cache partition in SPR....
But that didn't change the amount free one bit.
I also deleted every app I don't use. I literally only consistently use about 30-35 apps though, not a ton. I have 20MB or so tied up in Homerun Battle 3D but a lot of my apps are very minor, like a unit converter, etc.
Maybe 31.18MB is nothing to be concerned about, but it seems like an awful little space left for the future.