OK, so it's officially over between us. Now how to tell him without him going suicidal?

Well, I no longer think my relationship is going anywhere and I want to break it off. He is still really into me - at least I think he is and he can be a very sensitive guy. How do I break it off quickly but not mean? I'm sure if I do it in a good way we can still salvage a friendship but wrong and he may be scorned and hate me. So any break-up experts here?

Updates
FYI - we've been together for a LONG time so this isn't just something that's a couple months old...