User blog:CrashySmashy/Private Servers?

I was looking for a way to play more customized LoL games, and I found sb mentioning private servers. There is a site where most popular servers are listed, but I have not yet found a way to play them (wasn't really interested that much into the search tbh).

1. Are there legit/legal(?) LoL private servers? Have any of you played on one?

2. If there are, what are the differences/possibilities?