Shoutbox

There are some trusted ones:
http://blockchecker.msnfanatic.com/

Is know the above is safe. What you have to realise is block checkers just check your contact's status, but not if they have actually blocked you. However MSN Messenger had the option to disclose your status, and thus you can hide your status from anyone outside your contact list .

This is why block checkers are not very effective any more.