- Bring a box and put odds and ends in it.
- Send out a "Thanks for the good times" email to the broader company org who you interacted with(if you haven't already).
- Tune up any last minute documentation for your projects.
- check that all source code has been pushed and any documents of interest are shared with relevant co-workers.
- Add personal contact info to the wiki if you have one, in case someone needs to get in touch later.
- Go 'round to the office and shake hands with people you knew.
- Leave at 5 or so, do so with friendliness - agree to drinks/dinner with anyone who asks.
If this is not the case, then the usual list of recommendations for leaving a job apply, just applied faster and more selectively. :)