I have tried the die and assorted stuff but It seems like I can never find those small nagging A/C leaks.

Any good ideas?

Wish I could help, but I sometimes find myself in the same boat. My source from whom I could borrow the sensitive sniffer (which helped about 50% of the time) moved away. My last try with the UV dye to find a slow leak met with no result (other than me longing for my youth and old teenage bedroom with the Zonk and SuperPeace posters).

I ended up taking the percentage bet, and throwing a [thankfully on hand, good used] compressor at the problem. It fixed it.

So I guess my constructive contribution here is to

I do believe a FLIR thermal imager would be the best, quickest, and posibly most expensive.

some ppl down here uses a soapy water to get wet all the lines and fittings to check for bubbles...

of course thats not posible on crank seal, but works fine on the rest

My brother-in-law made a fitting that connects to the a/c lines & allows you to fill the system w/ compressed air-usually about 40-50 psi. All you do is listen for leaks. I used the fitting on my '91 Dakota w/ r-12 & it helped me find the leak in the coils buried in the dash. Like you, the dye didn't help me find the leaks that are buried.

Know the system and the problem areas.
Most leaks are at the fitting seals, the compressor shaft seal or other places where 2 parts come together. There are also evaporator leaks and condenser leaks (more common), hose leaks and ceacked lines (less common).
The leak checkers are better than the dyes, but different leaks require different tools. Have and use all of them.

I know this is a bit OT but it's A/C related. When my dad passed, he left me his tools and and such. Among them was a A/C recovery vacuum and A/C gauges etc. I went to use the pump and found that it didn't work. Went to my local auto parts store to see if they had one I could rent. The guy I usually deal with spoke softly and said, "I didn't tell you this, but hook up your gauges and the one you would hook up to the pump just hook it to an engine vacuum and let the car run until the gauges run negative vacuum. Add freon and your good to go." Well I don't know how common this knowledge is and I know how illegal it could be and I'm not saying I actually did it so DAMHIK it works but it "probably" does! Now remember, "I did NOT tell you this" The system didn't have any freon to leak into the atmophere anyway because it already had Warm air was blowing on "Max A/C" hence the need to vacuum in the first place

Scott Carl, since you didn't do it , I will add this for those that might try; burning refrigerant creates phosgene. VERY nasty stuff!!!!

http://wiki.answers.com/Q/Phosgene_gas_exposure_from_working_with_freon.

Some A/C shops recommend leak testing with nitrogen when all else fails.

if youre not using those yellow tinted glasses when looking for leaks using the uv dye I would suggest picking up a pair of those. They make spotting the leak 100x easier