For PG and VG I use Amazon
For flavors I use Wizard Labs, The Flavor Apprentice, and Central Vapor for concentrates of a few of my favorite premixed flavors.
For Nicotine (in 100%VG) I use Central Vapor
If I was looking at a pre-made mixing kit I'd use Central Vapor, however I had all my beakers, syringes and such from teaching Chemistry so I didn't need to purchase much. When I do need syringes, I go to my local feed store because they're cheapest there and they're the exact same that you'd get anywhere else. For anything science-y I use homesciencetools.com because they have good prices and quick delivery.
A good DYI site for recipes/ejuice calculator etc is: http://www.kritikalmass.net/
Just remember what tastes good to one person might not taste great to another...It IS subjective