One more HD DVD player is expected to be released this month: RCA HDV5000. The player is very similar to (and is most likely based on) Toshiba HD-A1/D1. Attached is a preliminary Spec from RCA's website. It is very similar to Toshiba's, though I do see some differences (e.g. DVD+R/RW is explicitly mentioned as supported with some exceptions, RS-232 connector mentioned, etc.)
The player will be sold in Circuit City and other retailers. The CC website takes pre-orders and shows 05/23/06 as expected ship date.