a few more to add for Vegas:
Palace Station $8
Palms $8 & $25
Gold Coast ncv 25 (these are hard to find)

Bellagio also had a $8 last year for the first time, not sure if they'll do one again this year.

Non-Vegas:
Harrah's Reno $8
Hollywood Park, Ca $2.50, $5 & $8
Commerce, Ca, $5 & $25
Cache Creek, Ca, $8