I have run campaigns with other folks' homebrews, to an extent, but I haven't really had a consistent group. Since moving to Arizona, I've only been able to play D&D over the OpenRPG program, joining or forming online groups to play or DM with. With Emiricol's group, I've played in his Bandora homebrew as well as The 13 Kingdoms, and then I ran a campaign in The 13 Kingdoms (the Adventures of the S.S. Fortuna, a good/neutral privateering/seafaring/treasure-hunting campaign).
I also ran gladiator matches in The 13 Kingdoms for a semi-consistent group of PC gladiators (a few of whom played in enough matches to gain a level or two). I've also played in a few T13K games besides, and I took over Emiricol's T13K campaign "For More Than Glory" for a few months or so, while Em's been too busy to game much lately. Now Firehorse/Valdir and Memnus/Fleck alternate DMing the FMTG campaign while waiting for Emiricol to regain enough free time to DM. If I ever have enough consistent computer time again, I'll be trying to resume my old Fortuna campaign or start a new one and take over as Council Member of one of the unclaimed Kingdoms; far as I know, Hibrideas and Cryndon haven't had a CM since T13K's initial setting creation was completed, while Argossea and Suryanasta only briefly had CMs; the other Kingdoms have had longer-lasting CMs, but only a few CMs are still semi-active right now. Council Members devise updates and new descriptive material for their Kingdom, and are sort of like overseers but pretty much don't interfere.
I've been unable to DM or play though for the past half year or so, now, so I had to drop out of my T13K groups and stuff at least temporarily. For those not in the know, The 13 Kingdoms is essentially a collaborative homebrew setting for 3E/3.5E D&D that was formed by former Living Web DMs like Emiricol, Silverglass, Entropy, Reckless, and others.... I never really had any hand in creating the setting, and only found out about it from Emiricol as he put his Bandora campaign on hiatus to begin running a T13K campaign. I've only contributed a few little things here and there to the setting after-the-fact, when DMing briefly after T13K had been running for a year or so.
T13K is a "living" campaign setting itself, so for instance, my PC dwarf Theodus Brightbeard was able to transfer over from Emiricol's first, short Kinrisar mini-campaign, into Entropy's longer-running Kinrisar campaign some time later. Occasionally the Council Members post updates regarding events in each of the 13 Kingdoms. For instance, when my first PC in the For More Than Glory campaign, Magnus Krieghelm, died in the act of delaying a goblin army (not horde, but rather a true, organized army) from assaulting a town in his home nation of Mittendien, buying time for the rest of the party to organize an evacuation and further delay the goblins until finished, Magnus' sacrifice and the subsequent destruction of (evacuated) Tillich was noted in the next update of the timeline.
Unfortunately, T13K is all-but-dead for now, since most of the setting's creators have been too busy IRL or with other campaigns to really serve as T13K Council Members, and the active DMs in T13K have mostly been caught up in important stuff of their own IRL and unable to continue their campaigns, such as has happened with Emiricol and Entropy (and those are just the ones I know for sure have been busy with important RL stuff). Firehorse and Memnus are keeping Emiricol's group together and gaming still, but I wasn't able to stick around right now and Emiricol's likely to remain busy IRL for another year or two I'd bet. Entropy might be able to resume his Kinrisar campaign soon, but I dunno. The Council Member for Rhaavin (I keep forgetting his name somehow!!
) has been working on starting up a Rhaavin-based campaign in T13K, but as far as I know he hasn't had any luck yet in getting together an online group for that; he was running a tabletop D&D campaign though in T13K, but as such, I don't know what kind of campaign it was, since he didn't use the online forums of T13K at EN World for his group's OOC or IC discussions between sessions.
. I have in the past used ideas from other's homebrew. Amusingly enough it was the link in your sig that got me to ask the original question to begin with. As I got looking through them they all seemed so painfuly vanilla (oh look the elves here are haughty, and beautiful, and attuned to nature too :\ ). To be fair though I didn't go in depth with every one, so I'm sure there were some good ideas that I missed. 
