I used to always send out my slides to Fair Lawn, NJ (I started regularly using slide film in June 1999), in the last couple years though, I gave up on shooting Kodachrome Film for the simple fact that my only option for processing involved a 3 week waiting period by sending it out with the mailers. I now use a Professional product from Kodak, an E-6 film called Kodak E100VS Pro, this is by far the best slide film I've ever used, I honestly believe the color quality is as good if not better than Kodachrome! I know this will spark some debate, but it's the only slide film I've used now for the last 3 years! I've tried a couple other Kodak products but like the E100VS the best. I also take all of my slides to a place called Color Tech on Sheridan Drive in Amherst, NY, they are a certified Kodak Q-Lab and a roll of 36 slides (E-6 Processing) costs like $7 or $8 for 2-hour processing and they use the good plastic mounts on the slides.
For anyone in Western NY, here's their web site: