X-Perl Unitframes is another that gives party casting bars along with lots of customization of your character and party UI. It replaces Blizzards default unit frames. You can see your target, your target's target and all your party member's targets.

Its got a lot in it, most of which I haven't explored yet. One thing I noticed last night is that it puts countdown timers on the debuffs on your target, like a warlock's curse. Handy to know how long before you need to reapply.

http://www-en.curse-gaming.com/downloads/details/3416/