Hello, check out this:
http://www.deccanherald.com/deccanhe...92005/spt9.asp
It's a article on diffues irrigation using a mud pot. Mud pot's are
porus and leech moisture in to the soil..MInd you, i don't know if it
works so..

Also check out: http://www.irrigationtutorials.com/. He's got stuff on
drip irrigation.
Don't neglect the wikipedia; you may find stuff on reference article's