Found some usefull plugins...

I was just checking Bukkit and stumbled by some interesting plugins (Notice that I did NOT test any of those , so you need to find out if it works or bugged first)

here are the links to some:

http://dev.bukkit.org/server-mods/fruitful/
perhaps put some coca beans in gravel ? or whatever comes in your mind ..

http://forums.bukkit.org/threads/admn-sec-xray-informer-2-1-5-protect-your-server-from-x-rayers-cb-1-1-r3.33737/
I've done my studies and I've noticed that there are many xrayers than you could imagine .. Almost half the community of each server are using Xray , So hope this helps to get rid of some..

http://forums.bukkit.org/threads/sec-rules-v1-1-whitelisting-via-rules-1240.9172/
Might be annoying to some people ... Idk

http://forums.bukkit.org/threads/fun-partyhat-v0-3-lets-you-place-any-block-as-your-helmet-1-1-r3.25891/

http://forums.bukkit.org/threads/fun-rpg-mobdisguise-v1-7-transform-into-any-mob-and-players-too-no-client-mods-1-0-1-rb.28750/

and these two last ones are just for fun lol
I'll be looking for more in the near future