Editing
My main interest is in miscellaneous cleanup around the encyclopedia. I copy-edit for grammar, clarity and brevity, adjust links to ensure that the transition between related articles is as smooth and topically heirarchical as possible, add hatnotes and templates and post messages on the talk pages of obscure articles listing what I'm too lazy to do.
Efforts to organise the encyclopedia into a more productive and comfortable place for its editors are more important now than ever. Productivity-wise, the Task Center, Dashboard, open task list and maintenance resource list are evergreen sources of articles that require correction. Articles for Improvement might be the best, though. I think that more articles should have to-do lists.
This is my favourite Wikipedia essay, and I love this massive, categorised index of free virtual gifts to give to other Wikipedians.
It may be the world's biggest encyclopedia, but it still has a Contents page and an anime mascot.
See also: WP:IOC, WP:AGF, WP:DDMP, WP:SPIDEY, WP:SURPRISING, WP:WIKISPEAK (especially 'userbox'), WP:ODD and WP:LAME.