GW2DB

Instead of directly farming these another great way to get them is by opening the "Moldy Bags" in the game. These have an extremely good chance of giving you a fine crafting material (a blue one, like this one) and are rather cheap on the Trading Post. Usually ranging from 20 - 50c a bag, depending on the type of bag.

While you won't get rich buying bags, opening them and selling the reagents on the Trading Post you definitely will be able to stock up your collectibles tab at an insanely fast rate. I made a video on how this method works, if you'd like to see it: Fine Crafting Material Farming Video for all skill ranges.

Here are a list of all the bags in the game so you know which type you'll need to buy for whatever item you're after.

Tiny Moldy Bags (0 - 50 Components)

Small Moldy Bags (25 - 100 Components)

Light Moldy Bags (75 - 175 Components)

Moldy Sacks (150 - 250 Components)

Medium Moldy Bags (175 - 300 Components)

Large Moldy Bags (300 - 325 Components)

Heavy Moldy Bags (325 - 400 Components)

Very good spot is in Godslost swamps killing fireflies, they are neutral and easy to kill. Drop is very nice

https://docs.google.com/spreadsheet/lv?key=0AnHPcS64MRxrdG5scTNUaVp4aWlsMTAyaktHeWo1YkE&pli=1&toomany=true#gid=0

There you go, the table

Love the spreadsheet, keep up the good work :)

Additionally, here are a few monsters, their locations, and the speed at which you can farm them for Tiny Venom Sacs.

Grub - Altar's Windings (Queensdale) - Fast
Spiders - Shaemor Fields Apple Farm (Queensdale) - Fast
Cliff Bats - Bandithaunt Caverns (Queensdale) - Medium
Firefly - Godslost Swamp (Queensdale) - Medium

These are just some that people have had good luck with farming. I got these from a Google Doc posted somewhere on reddit... Sorry I do not remember the source. It's a community doc, though.

/r/north

Best way to farm these is killing Lashtail Devourers and other creatures in that family, basically anything that looks like a scorpion but with 2 tails.  Higher level ones will drop different venom sacs though so keep to the lower level zones.  The best area I've found for it is directly north of the Black Citidel, in the area north of Town of Nolan.  Just stick to the rocks and walk north and south killing them along the way, respawn is decent enough.