Nearly all my flavoring comes from ecigexpress.com
I'll look at the other sites mentioned if I really want something and ecigexpress is out of it, but most of the time I can wait, especially since they carry most flavors in larger bottles.
Syringes and (if you want them) graduated cylinders can be bought pretty cheaply at amazon.com
Especially cheap if you buy them in big packs. Like a box of 100 syringes for under $10. Much better deal then paying half that for only 10 at other places. If you buy the blunt tip needles separately (the big packs of syringes don't come with them), they are sold in packs of 50 for around $10. Lets you select a few different sizes based on your needs. Like thinner needles for extracts and thicker needles for nicotine.
I get all my VG and PG from essentialdepot.com
Nic from vaperstek.org
Bottles, well, that one is a bit messy.
The bottles I use for my own *personal* liquid is this combo set:
http://www.sks-bottle.com/340c/fin21c.html
But, I use the caps from these
http://www.amazon.com/gp/product/B00B513AKA on the 120ml and 240ml bottles
Offers the best of both worlds. The sks bottles are great, I love them. But the caps aren't the best. The twist caps are easy to use, but they can leak easily. Liquid will often remain in them after dripping and if the bottle warms up, it will squirt out when opening the cap. You can avoid this by leaving them open if your going to be using the bottle often, but then after a bit of time liquid will seep out around the twist portion and drip down the bottle. Any liquid in the twist portion can come out when shaking the bottle as well. It's also easy to over drip with twist caps.
The amazon bottles are stiffer, harder to squeeze and the measurements on the side are completely useless. But those caps are wonderful. They don't leak at all and it is easy to control the amount of fluid coming out. They only fit on the 120ml and 240ml bottles from the sks combo set and I am always swapping the few I have around on the bottles depending on what I feel like vaping.
I also have a bunch of regular (non-opening) caps that I use on all the bottles from the combo set when not in use.
http://www.amazon.com/gp/product/B00TR1QYJO fits on the 30ml and 60ml bottles
Haven't found any that fit on the 120ml and 240ml bottles yet, but I haven't looked either since I have half a dozen or so that came with eliquid from back before I started DIY and they happen to fit on the larger bottles from the SKS combo set.