Ancient Celts believed the membrane separating this world and the underworld, or afterlife, became thin and was breached by various spirits on All Hallow's Eve (they traditionally called it Samhain, I believe?). See, Samhain is believed to have marked summer's end (the word derives from the phrase for that in Old Irish, supposedly.), and the border between the "light" part of the year and the "dark" part may have seemed related to a thinning of this barrier between worlds. The spirits who came through could be harmless, but were also potentially harmful. Costumes were worn both as a means to confuse the harmful spirits and - by young men - to symbolize the spirits of family who had crossed over, that viewers might remember those who had passed and respect their memory.
So...what are you going to wear?
Regardless, here's what you might want to do:
Ladyfag's new Clubber Down Disco returns for its second night with Honey Dijon DJing and Tai Chi, One-Half Nelson and Casey Spooner hosting. Ryan Smith at the door, whore! Word to the wise? Arrive on the early side. There's more than one reward (i.e. - entrance) awaiting you if you do.
Similarly, Mr. Rich King and Mr. Gustavo Motta offer incentive to arrive to their Snaxx shindig early. They'll be wigging out (as you should be!) but the beer will be free (from 10pm - 11pm)! Also popcorn, peanuts and a surprise!
Uptown at mine and Tai's (well, EVERYone's) old haunt - Rebel - Peter Rauhofer and the WORK! crew (DJs Corey Craig & Nita Aviance spin upstairs and Ms. Roze BLACK is BACK hosting the party!) throw a night of Hallo-weenie craziness.
Bana is back, but they've been kicked out of their Downtown Fulton Street baths location at the last minute so are moving the VIP portion of the party out to Brooklyn to the site of the original banya party several years ago that kicked the whole shebang off. The baths there are SITTing, is all I'll say. Oh and transportation is provided (via go-go equipped...or equipped go-go? party bus.) from 15th and 8th Avenue (in front of Starbucks) three times: 11pm, 12am, and 1am with two return trips at 3am and 4am. I think you may have to already have a ticket to ride the bus, so hit up the website for full information and the ticket purchase link.
There's (what seems like) a thousand other options, as well. Find the FYF Calendar for those.