In general, it's very productive to search 122.000-123.600
Here are a few categories:
Air-to-Air: These are the truly legal channels, but I generally don't hear a lot of chit-clat. In the Washington, DC area (pre-9/11, of course) aircraft flying in the Class B airspace's VFR corridors were supposed to monitor 122.75 to avoid collision.
122.750 (fixed wing)
123.025 (helicopter)
Flight Instruction: Much of the legal use is with gliders and ballooning. Very good prospects for unofficial chit-chat.
123.300
123.500
121.950 (secondary to Aviation Support, I think)
Aviation Support: There are all kinds of uses for this, including fuel trucks at airports. I hear a fair amount of chit-chat on 122.775. 122.85 is fairly quiet in my area because several air bases around DC and Hampton Roads use it for Pilot-to-Dispatcher. (a military use similar to Unicom)
122.850 (secondary to multicom, I think)
122.775
121.950
Multicom: These are fairly wide open frequencies intended for air/ground comms supporting air/ground activities.
122.900 (often used as CTAF for uncontrolled airfields with no Unicom)
122.850
122.925 ("environmental"... this often translates to "governmental")
Flight Test: heavily abused. Most of the freqs from 123.125-123.575 that are not otherwise allocated. 123.4 and 123.45 are famous examples. You might also hear some military air/air in this area.
That may provide a little coloring for you. Less often heard are the two "domestic" freqs 122.825 and 122.875.
Best source for most of this would probably be the current Airman's Information Manual.
I used to greatly enjoy listening to 122.775 in the days when there were flights carrying cancelled checks around the country at night. There were a lot of regulars on the air.
Don't forget that there are plenty more freqs out there. These are just the ones that actually have defined uses.
73/Allen (N4JRI)