Adjective used to describe a
web site that draws
repeat visitors, usually by virtue of good
content and the absence of bad
design.
There's more to stickiness than just content, though. To be sticky, a site must be so compelling and immersive that the visitor becomes nearly a resident. Sissyfight, E2, and Hot or Not? are all pretty sticky.
Note for the innuendo maniacs out there: a sticky site is not necessarily related to other sticky stuff.