A San Diego group has created a series of cards that you can use to (at least semi-) tactfully tell your neighbors to water their lawn, keep the nopise down at night, etc. Some of the messages are actually kind of funny.
This work is licensed under a Creative Commons Attribution-
The Geek Code desperately needs updating, but in any case here's mine (as of 2010-02-28):
-----BEGIN GEEK CODE BLOCK-----
GIT/MU d+(-) s:+>: a C++> ULXB++++$ L+++ M++ w--() !O !V P+ E---
W+++ N o++ K? PS PE++ Y+ PGP t !5 X- R- tv+@ b++ DI++++ D--- e*++
h--- r+++ y+++ G+
------END GEEK CODE BLOCK------
If you really care about knowing what that all means, you either know the code already, or you can get it decoded for you here.