Vista sidebar is useful sometimes. KDE doesn't have a sidebar. However last night I was working on a Karamba theme and I made this sidebar. I used existing themes, I merged them in only one file and this is the result.
This sidebar is always visible when i maximize a window but if a need a little more of space i can put windows over the sidebar.
I need permission of some karamba developers to upload this theme. But I think is cool.
If I can do this with KDE 3.5 maybe better stuff could be made with KDE4.
I think that something like a sidebar could be implemented in KDE4. This could be like an ontop space to put useful stuf. A calculator, contact manager, rss, etc.
Please sorry for my english.