Currently, LG's BH100 is the only DVD player that can play both HD DVD and Blu-ray discs. That might change soon, however, with Samsung's Duo HD BD-UP5000. The rumored player is expected to be compatible with both high-def DVD formats, supporting all of their features like Blu-ray (BD-J) and HD DVD (HDi).
It'll also support all of the new high-def audio formats and come with an HDM 1.3 output. Pricing is still up in the air, though if they wanna get people's attention, my advice is they try to keep it under a grand.
Rumors of a Dual-format Player from Samsung [Home Theater Blog]