Mouser, Digi-Key and the like. For a few pennies less, you can go with others like JustRadios and the like, but for me, I stick to Nichicon, Pansonic and Nic Components caps. Just better quality, based on my experience.
What caps do you need that are unavailable, unless in 1K quantities? I have a deep stock of stuff for my use, but have a whole list of suppliers for specialty caps:
Low Voltage Electros - Talonix, multiple brands (Illinois Capacitor, Panasonic, Nichicon, Nic Components, some United Chemicon)
High Voltage Electros - for radials (all i use, can't afford Sprague Atoms) - I use Panasonics from Digikey and Mouser. Mouser ships quickest.
High Voltage axials - Allied, under the ASC brand - also check out their excess stock. I get a few things that way time to time.
630V radials - Digikey, Panasonic brand, and Mouser, they also carry Panasonic ECQs
With Digi-Key, if you prepay by check, there are no shipping charges:
http://www.audiokarma.org/forums/sho...26&postcount=1
I've used the free shipping for all but one order that I needed quickly, and I placed it via the web, and paid only $5 shipping.
Get some experience using Mouser's drill down search (Passives, Capacitors, Electrolytic Capacitors, voltage needed, value needed, and ALWAYS check the "In Stock box") - that'll give you a part number, and check the price over at Digi-Key to see if they are cheaper. I stress Digi-Key, because with multiple parts orders a year, I can save 30-40 bucks in shipping with their free shipping.