Here’s a list of the sites I’ve heard are worth checking out:
Thanks Adam S:

• Kay Op in Tulum
• Dosojos (2 cenotes there Bat Cave and Barbie Cave)

Here’s some notable cli entries that I refer to occassionally:

Mac OS X:

sudo /usr/sbin/sysctl -w net.inet.ip.fw.enable=1
sudo /sbin/ipfw -q /etc/firewall.conf
sudo ifconfig en0 lladdr 00:1e:c2:0f:86:10
sudo route add -net 10.2.1.0/24 10.3.1.1

Linux: