Synaptic

Synaptic Package Manager is merely a GUI for apt-get. So it may prove useful for user-friendliness.

I don't think it's necessary if you have GDebi. Just get used to searching the Ubuntu Packages list under distribution Hardy (or whichever base you are using), double-click the i386 file, and select a mirror to download from.

Provided you can then find the package to double-click on it, GDebi should sort out all your dependency issues for you.

Nevertheless, it also allows updates to be done via GUI, so you may want it…
sudo apt-get install synaptic

Another potential option (albeit with even more dependencies) is to use apturl

apturl allows a website to include links to install packages (with dependencies) directly on the surfing machine. You could then potentially borrow the OzOS apt:foo list to double-click applications to install.

To install apturl (and its dependencies):
sudo apt-get install apturl

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