Go to The Honeynet Project and take a look.
Having done this a few times, I assure you it's really not necessary to tell anyone about the box. Attackers will find you. I've seen honeypots of mine compromised literally within hours of being plugged in.
In fact, I voted -1 on this because asking to be hacked in a public forum is a very bad idea. Doing this will get you 0wned, but to a lot greater extent than you're expecting. Not wise. Again, they will find you.
You also need to look into firewalling this box off from the rest of your network to prevent the domino effect via your packet filter / proxy of choice, and logging the traffic via some sort of logging mechanism or other. Snort, Pakemon, and TCPdump, or any combo thereof, will work.
Read Bugtraq, the Incidents list, the Pen-Test list, CERT and NIPC advisories, and Packetstorm, maybe poke around in EFFnet a bit, and you'll figure it out.
Point being, there are a tremendous amount of resources to draw on from a lot of folks who've been doing this for a lot years, and what you're proposing has been proven time and time again to be ineffective and unscientific.
Drop a box in, tell no one, and let it be found (and it will be). No need to be so ham-fisted about it. Try to think like a clueless admin, and make as many obvious mistakes as possible without making the box look staged.
Good luck and have fun.
BTW, for an OS, it's more or less immaterial-- anything will get compromised eventually, although more widely-used apps and platforms will have more widely-used exploits. Choose whatever platform you're interested in learning about security on.
"Somehow we get by without ever learning,
somehow no matter what the world keeps turning"