I've tried by directly ordering through the supplier (in approximate chronological order):
Dekang
Ms. T's Bakery
Johnson Creek
Tasty Vapor
FSUSA
Backwoods Brew
Kick Bass Vapor
Vaperite
Alien Visions
Vapor Station
Prime Vaping
Bluemist Vaping
I've tried via trade or the like:
Want2Vape
Goodejuice
Joogler Juice
Bombay Vaping
Vapenine
My favorite:
Alien Visions
Backwoods Brew
My favorite is a tie between Backwoods Brew and Alien Visions. They are both offer such amazing, unique, superb quality products that I can't choose between the two. I'd really miss both if either one disappeared tomorrow. I use more and a greater variety of the BWB juices but AVE's Boba's Bounty is just so singular and amazing that AVE will always have a place in my vaping habit.
Keeping in mind that taste is very subjective, I'll say the following about some of the vendors I will not buy from again:
Johnson Creek - All of their juices are more or less indistinguishable from one another and have a musty sock funk to them. Customer service and packaging are amazing, however.
Ms. T's - Expensive, slow shipping, only offers dessert-type flavors which are not my thing. Great customer service and very high quality, well-performing juices, however.
Bluemist Vaping - Really foul roundup-type chemical funk to the caramel tobacco flavor. Once tasted, it cannot be untasted. Great service and impossibly low prices here.
Bombay Vaping and Goodejuice - All of their juices, even post-steeping taste like perfume. Yuck.
Did I mention that I really like BWB and AVE?