Clickable Signs in Minecraft

Paste the following into a command block to create a clickable sign, fiddle with the commands yourself to try new things =]

Say something when clicked:
/setblock ~ ~1 ~ minecraft:standing_sign 8 replace { Text1:"{ text:\"Click.\", clickEvent:{ action:run_command, value:\"/say Clicked.\" } }"}

Adjust a score when clicked:
/setblock ~ ~1 ~ minecraft:standing_sign 8 replace { Text1:"{ text:\"Click Me\", clickEvent:{ action:run_command, value:\"/scoreboard players add @p signs 1\" } }",Text2:"Add score"}

Place a Redstone block when clicked:
/setblock ~ ~1 ~ minecraft:standing_sign 8 replace { Text1:"{ text:\"Click Me\", clickEvent:{ action:run_command, value:\"/setblock 152 7 20 minecraft:redstone_block\" } }",Text2:"Power Redstone"}

Join Red Team:
/setblock ~ ~1 ~-1 minecraft:wall_sign 0 replace { Text1:"{ text:\"Join\", clickEvent:{ action:run_command, value:\"/scoreboard teams join Red @p\" } }",Text2:"Red Team"}

Leave team:
/setblock ~ ~1 ~-1 minecraft:wall_sign 0 replace { Text1:"{ text:\" \", clickEvent:{ action:run_command, value:\"/scoreboard teams leave @p\" } }",Text2:"Leave Team"}

Join Blue team:
/setblock ~ ~1 ~-1 minecraft:wall_sign 0 replace { Text1:"{ text:\"Join\", clickEvent:{ action:run_command, value:\"/scoreboard teams join Blue @p\" } }",Text2:"Blue Team"}

If you want to know more about JSON for chat, books, and signs please visit this page
http://goo.gl/KggvyK