Crosswords
In my third year at uni, I set cryptic crosswords for TCS under the name Apis (and on occasion, thanks to editorial whimsy and cock-up respectively, the names Martkay and Cherbury.) Some of those crosswords may be found, in delightful Java-applet form with downloadable PDFs for those who like to do things properly, at Apis Crosswords.
I also run apisclues on Twitter. A new clue goes up every weekday, and every week’s clues are connected by a theme. The solutions and the connection are revealed at the weekend, and correct solvers score points according to a system as devilishly arcane as it is made out of meringue. Top scorers receive glory and perhaps even an invitation to eat delicious delicious chilli.