People seem to have already covered the basics, so here's some
great thrashy stuff that you need to hear, but hasn't been mentioned yet (some of this may venture a bit into the heavier than thrash, but all of it at the very least has thrash/speed metal roots)
Coroner
Amazing technical thrash, the likes of which few bands can compete with.
Cynic
The first thing you'll say is "Holy Shit! This came out in 1993?"
Great jazz inspired technical thrash with some interesting digitized vocals
Possession
The transitional period of thrash, as it turns into the roots of death metal.
Guitarist Larry LaLonde later becomes the guitarist for Primus.
Indestroy
Fun stuff, a bit like Metallica's first album.
Dream Death
Imagine Tom from Slayer singing for Celtic Frost.
Coven
The funniest thrash you've never heard.
Devastation
Forgotten thrash masters
Fear of God (not the grindcore band
)Greatest female-fronted thrash of all time.
Pantera
A bunch of redneck twats, but mandatory listening.
OK, you said keep it easy to find, but these are worth it:
Pentagram (Brazil)
Outstanding heavy stuff, imagine early Sepultura with an almost old-school black metal aesthetic.
Blind Illusion
What Larry LaLonde AND Les Claypool were doing before Primus and Possessed.
Wild, wild stuff.
Pale Creation
Out-f**king-standing. Ignore all of their later stuff and try and track down their first, and to a lesser extent, second demos. Possibly the greatest forgotten thrash band of all time, their first demo was AMAZING. Just AMAZING.
Puts a lot of their peers to shame.
