I was just wondering where I can find some good Fallout 2 mods. Are there any major sites? (similar to FO3Nexus) And are there any "essential" mods? Thanks in advance.

http://falloutmods.wikia.com/wiki/Fallout_2_Mods

I found this... I just picked up the trilogy last night though, and haven't played yet. I am sure there are others out there who can direct you better than I.

There's the fallout 2 restoration project but I don't remember the link.
It adds some new places to explore, new quests, ..., all based on what was intended to be in the game but was cut from development.
You should check if it integrates the latest unofficial patch, otherwise this would be a good download too.
There's also a mod to play in higher resolutions but I haven't tested it.

www.nma-fallout.com

Go to community, downloads, Fallout 2 mods.

plenty to choose from.