If you look around on the live map, you can find a bunch of wild outposts that you could explore. I'm sure that the owners wouldn't mind, as long as you don't take or damage anything.
You can find a village, trade with villagers until you can get a woodland or underwater map and raid the bases. make a small base with friends and everyone turn on diff 10 - allow boss and enranged mob spawns in "/ps" and try to survive a few minecraft days. Go to miner mania events and ask to turn group diff to 10 (the first and only one I could go to did that XD) IDK just a few ideas
Check out the LLO on smp7. Its one of EMC's first outposts, and is absolutely massive. Not too far from spawn either