This one, Urban Dictionary (at www.urbandictionary.com). It is made of random entries (like mine), may be offensive or X-rated, but still entertaining for me.
Pseudodictionary: Another slang, random-entry dictionary (at www.pseudodictionary.com), (much smaller than this, 25,000 smaller than a real dictionary compared to this, actually bigger than a real one). You may expect slang dictionaries to be smaller than real, like the Pseudo, but instead Urban's bigger. Pseudo rejects X-rated figures, swearing (unless they use the word in an acronym)
Dirt-tionary: (at www.mottie.com/dirt.html) Don't forget the dirt.html because regular Mottie isn't the Dirt-tionary. Dirt-tionary only has 68 phrases, and it's so sexual, I'd be really offended by the sex slang.
Double-tongued: Yes, it's slang, but it is written by an English lexicographer. If it weren't for slang, it'd be real. At www.doubletongued.com
Unwords: at www.unwords.com. Also in paper, like Urban Dictionary, you, unlike Urban, need the security-code on the bottom.
Redneck Dictionary: book, not website. Has pun words.