D**khead ex friend.. What would you do?!?

[dhkm3939]

So I've known this guy for like 3 years. We dated a bit when we first met but have just been friends ever since. Over time, I've lent him money and he's had other girlfriends and during that time, he has still "hung out" with me and afterwards i'd find out he still had a girlfriend. He has treated me so badly and i've gotten to the point (and this is going to sound stupid) where i've wanted to block him from facebook but i just haven't been able to do it.
The thing is, now (for some reason) he has blocked me and it actually makes me really angry that he got to do it and i didn't do it when i had the chance. I know it's just facebook and it's stupid but i kinda feel like he got the last laugh.
Even though all i've ever done is help him and i've never said anything to his current girlfriend or any of his past girlfriends about us so i don't know why he has gone and done it now.
What i feel like doing is messaging his girlfriend to tell her what he's really like. That's something very immature and i would never normally do anything like that but i feel like enough is enough and it's not fair he gets away with being an absolute dick!
What would you do?! I've also got a pair of his boxers and undies he left behind last time i saw him.. I'm tempted to txt him and say something like "So did you want your boxers & undies back.. should i throw them out or do you want me to ask your girlfriend?" and see what he says... What i'd also really like to say to him is something like "Guess i'm never getting any of the $800 you still owe me" .
What i'll most likely end up doing is just letting it go because he's so not worth it but part of me realllllllly wants to say something after all this time!!
I have actually tried to get the money from him before with friendly txt reminders but nothing has come from it. Might just send him one last text and then let it go and forget about it if nothing happens! You're so right MiX (below).. KARMA KARMA KARMA