Personally I really like what Reaper does. Different lists for instruments and effects, a list for recently used plugins, and the best thing is you can make as many sub-lists for organizing them as you want (Reverbs, Guitar, Mastering, UAD, Waves etc.).
There's also a nice right click context menu for bridging, firewalling and troubleshooting options.
Obviously there are bigger fish to fry at the moment, but some improvements here would be welcomed very much.
