A-Dock
 

I used A-Dock in OS9 (it was basically a docking program) and loved it. It is now available in beta for OSX and I will use it over Apple's dock (especially when all features are enabled).

Spring-loaded folders, Hide All (just one click, no modifiers), more customization features than Apple's dock...etc.

I am not affiliated in any way with the author, I just like the product.

Ciao

i'm using a combination of DockDisks and Cocktail's Hide Desktop feature. (Yeah, I know there are other ways of hding the Desktop but Cocktail makes it so easy.)

I also have all Downloads go to a Downloads folder in my Home directory. Keeps my desktop nice and clear.

Ultimate Drives Dock Popup
 

I've used DockDisks and really dislike how it quits/re-launches the Dock. Some time ago I found an article on creating a similar solution that doesn't require relaunch. I don't know who wrote it and I take no credit for it. I use it in Jaguar, and the only downside is that my HD icons are ugly aliases instead of custom icons. Anyway, its easy to try and doesn't seem to cause any problems. However, it does not implement spring-loaded action as the original poster desired.

...
Ultimate Drives Dock Popup
This tip creates a custom icon in the dock that will display all volumes, including removable media.

1) Launch Terminal and type:
cd /Volumes
ln -s "/" "YourOSXDriveNameHere"

2) Use the Finder's "Go to Folder..." command under the Go menu.

3) Type in /Volumes. Hit Enter. It should open a "Volumes" window with your mounted drives.

4) Select Column View for that window.

5) Drag/alias the "Volumes" somewhere safe, such as your users folder.

6) Paste an icon onto the alias, rename it if desired and put it in the Dock.

Notes:
- You could seemingly add symbolic links to other things in Volumes as well.
- I don't know if there's a unixy reason to NOT store things in /Volumes
...

EDIT: a MacOSXHints article seems to refer to this technique on MacNN, but the MacNN link is dead: http://www.macosxhints.com/article.p...=ultimate+dock

Another software option.
 

Springloaded dock items would be an interesting possibility. The dock is presently a bit quirky when dragging things onto it, so it might end up being frustrating.

--hunch-- It seems as though the dock would have to more thoroughly evaluate what each item on the dock was in order to know whether to and what to spring up. This might wind up slowing down some of the dock's other behaviors.--/hunch--

However, two options I didn't notice mentioned above (if they were, my apologies):

Ittec = boosts functionality of contextual menus and (I think) can include moving/copying/aliasing. (I don't use this one, but I might give it a try sometime soon.

MaxMenus = Adds user defined pop-up menus to keystrokes, screen corners, and/or the menu bar unused space. The ones in the corners can be spring loaded. Configuration is really simple. I've used this program for several months and it's been incredibly stable.

Sounds like A-Dock is worth looking into, too.