I have non-digital DirecTV with Tivo, but upgraded to a 50" Sony LCD Projection TV. I installed an antenna and am LOVING the digital/hi-def OTA stuff, but really missing the ability to use Tivo. Really sucked having to watch "24" on the low-def Tivo last night.

What are my options? I assume I can't use my existing Tivo to record OTA digital.

It's worth every penny!
Dish and Comcast have boxes also but I have yet to see a stand alone HD PVR in a store yet.

Directv is Digital. Your Directv TiVo is digital

What you want is a HD Directv TiVo - or a HD PVR that can record OTA. There are some computer hardware and software that will do what you want.

The best option out there is the Hughes Directv TiVo which has two tuners (like your SD TiVo) for Directv and it has two OTA tuners for recording HD OTA signals.