h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

No offense, but you can't even attempt to compile an American Slang dictionary without mentioning at least some of the slang that is derived from baseball. I am by no means an expert on the subject, in fact i only know a few terms, but I hope that--by broaching the subject--someone who knows alot more of it than I will step in.

Bases: a measure of what level of sexual activity one has participated in, usually used only by males in a cassual environment.
it varies from place to place, but this is the one I know
1st: making out w/a girl
2nd: "copping a feel"
3rd: fingering
Home Run: actual sex

Generally speaking, this is the single most famous (infamous?) part of baseball slang.

Score: to have had sex; to have succeeded at something; to have done something impressive.

Batting a thousand: to have done things perfectly, often used to signify the exact opposite

On Deck: next up

Don't forget what it's called when you don't score: Getting thrown out at Third base! I was caught stealing Second!

And don't forget those great terms for hapless or completely wrong: "Way off base" and "out in left field" - I think I have heard 'out OF left field' used for an unexpected event, remark or response - "That came out of left field". We have the 'three strikes' laws where a felon on his third conviction gets an extremely long sentence - often life - even if the 'third strike' was relatively harmless. In fact, 'third strike' generally means 'the last straw' or the final transgression that causes punishment to occur.

how about a bi-sexual being called a switch-hitter.