Anybody know of any good sources for tri bike frames? None of the major manufacturers sell just framesets, except for their top of the line one, at least not that I have seen but I could be wrong.
Any ideas?

Try competitive cyclist (online store). They sell most of their bikes as frames or complete packages. Brands include Cervelo, BMC, Look and others. I can't speak for individual shops but CC have a good range and have been great to deal with in my experience.

Tried Planet-X USA? I've always wanted to try one.

Leader bikes..or Ebay...frames are cheap . Heck an entire decent bike will cost ya $900-$1200

Thanks for the ideas. I checked out Planet-X and they have one I like the look of, but the seat tube angle is a little slack, 76 degrees rather than 78 or 79. What I really wish is if I could find a Cervelo P1 frame somewhere.
It just seems a shame to get a full bike when I have at least two bikes worth of parts in my garage, all Ultegra and several wheelsets.

The Planet X exocet is about $1100 and steeper than their old bike.

There is also:
Felt B12
Cervelo P2
Specialized Transition Pro

Those three are all about $1800 give or take. All well designed aero frames, available from any dealer I would imagine.

Another place is RAcycles. They have a ton of frames in the $1000-1500 range. I won't quite say they are as aero as the above, but good quality new old stock frames:
https://www.racycles.com/sales-center/triathlon

ha ha yeah I totally forgot about RA Cycles. They always have old backstop for cheap too.

Yes, IMO the P1/P2SL is still one of the best frames for the buck out there. I actually got a great deal on a used one right here on the forums - seems like there is always one floating about. Perhaps you could throw out a feeler if you decide that is the route you want to go.

Its a shame. I live in the SF Bay area, where cycling and triathlon is really popular, so deals on craigslist don't last long, so I have to be really on the ball to catch a good one. I am actually trying to sell my Cannondale CAAD9 bike, 2009 frame with 2010 ultegra on it right now for $1300 and already got like, 10 emails in three hours or so.
Basically, I used to do triathlons almost exclusively, but hurt my knee and switched over to just bike racing for about 2 years, now my knee is good and I am doing tris again but dont have a TT bike. I have two good road bikes, so I would still have a road bike for hilly or really long bike legs, and want a new frame to build up for flat courses.