First off, I'm running Dolphin 1.4 on KDE 4.4.5 (Kubuntu Lucid Lynx) so I admit I'm not on latest and greatest...

My current problem is that my "Places" panel is getting very crowded. To put some order there, I wonder if I could either:
- have the places arranged in a tree
- use three of four different "Places" panels (defined by a parameter in a shortcut, for instance)
Unless someone has an even better idea?

There is not much you can do. Just come up with a new idea and write about it on brainstorm. Here is similar idea
viewtopic.php?f=113&t=101268#p224591
You can use dashboard and create shortcuts to all this folders on dashbord or on your desktop.