Sporeggar

As you venture westard in Zangarmarsh, you'll eventually encounter some strange-looking mushroom men. As with the Kurenai and Mag'har, you start out unfriendly with the Sporeggar, but raising your reputation to Friendly is simple. Beyond that, you'll have to decide for yourself if it's worth it to aim higher.

WoWWiki - Sporeggar
Wowhead - Sporeggar quests

There aren't any gear rewards that are still useful at 70, and most will probably be replaced within a few levels, so you may decide it's not worth the grind. Alchemists, however, will at least want to get to Revered for the transmute recipe. Also, at exalted you can get a non-combat pet (if you're interested in that sort of thing).

Unfriendly and Neutral
Just through general questing in Zangarmarsh, you'll find yourself killing bog lords, first in the Dead Mire in the northeast, then later at Quagg Ridge in the southwest. The kills themselves will grant Sporeggar reputation, so you may find yourself close to Neutral without even trying.

As you're killing bog lords, however, hang on to any [Bog Lord Tendril] that you find. These are the turn-in item that's easiest to aquire, and will take you all the way to Friendly. Even without rep from killing (if you get the items from the Auction House or a guildmate or alt) it only takes 48 of these items to get to Friendly. With the killing involved, it will obviously take less.

You can also collect [Mature Spore Sac] from the Spawning Glen as an alternative. Both of these items are turned in to Fahssn, an NPC who wanders near the Spawning Glen, south of the actual town of Sporeggar. At Neutral, you can go into town and get another turn-in quest for [Glowcap] (these are found EVERYWHERE in western Zangarmarsh). With these three options, you'll easily get to Friendly reputation with the Sporeggar in no time.

Friendly and Beyond
At this point, pick up the quests to go into the Underbog: Bring Me A Shrubbery!, Stalk the Stalker, and Oh, It's On! The Shrubbery quest becomes repeatable, so grab as many [Sanguine Hibiscus] as you can, and continue to do so if you make multiple trips into the Underbog.

There is also a repeatable turn in for [Fertile Spores] (this actually opens up at Neutral, but the other turn-ins are easier to get), and a repeatable quest to kill Bloodscale naga. These repeatable quests are the main ways to increase your reputation to Exalted, since you get 750 reputation for each turn-in. This translates to 31.25 rep per kill of the naga, far more efficient than killing bog lords (which only grant 15 rep each). The average reputation rate for the Fertile Spores will vary based on drop rate, but you can also get these from guildies or buy them on the Auction House, if your time is more valuable than the gold it costs.

The bog lords will continue giving reputation until Revered, so that is still an option. Also, the mobs in Fungor Cavern give reputation all the way through Exalted, but the amount of reputation you get depends on the amount of help recieved from the Sporelings that also inhabit the cave.

Exalted
If you do reach Exalted, there is one final quest to obtain most of the rewards for this level. If you want the tabard, Alchemy recipe, or your pet, you can purchase that directly from the Quartermaster. However, if you want the [Hewing Axe of the Marsh], [Sporeling Claw], or [Sporeggar Smasher], you must complete the quest Fhwoor Smash!

This is a group escort quest. If you are at a low enough level where these rewards are still of use to you, you'll definitely want to bring friends along. I've personally never done the quest, but from what I've read, it's not one that can be soloed except possibly at 70 (when the rewards aren't useful anymore anyway).

Overall, Sporeggar seems to be a fairly pointless reputation to grind compared to the others, since it has no long-term benefits for anyone other than alchemists (or those who want a tabard or pet just for fun). If you do want any of the gear rewards, I would stock up on as many turn-in items as you can ahead of time, so that you can level up and get your rewards as early as possible, to get the most use out of them.