Mentioned a few places, but seems relevant here is Event Horizon (video showing it being used by a shadow priest:
YouTube - Event Horizon WoW Addon)
I really like FBN + Event Horizon, since Event Horizon is a just a nice way to see how all my bleeds are going, and what I really like is that it shows the mangle timer as a darker gray if an arms warrior or other druid puts the debuff on, so I can see who is actually mangling, and weather it's my mangle that's going to fall off, and I should probably plan to get it back on. (I run with another feral on my 10s, and no arms warrior).
The 2 together are very nice, and Event Horizon (for me at least) lets me predict what FBN will predict, which is good, since at this point I'm almost choosing the same thing in my mind that FBN is choosing for me.