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.