Zero Install is a simple platform which allows users to find and run some popular applications without installing them.
The program doesn't need installing itself, either. Getting started is as easy as unzipping the download and running ZeroInstall.exe.
A straightforward interface lists 80+ applications: Audacity, Blender, DOSBox, Gimp, KeePass, LibreOffice, Firefox, Media Player Classic Home Cinema, Nmap, PDF Split and Merge, 7-Zip, TightVNC, UltraVNC, CDBurnerXP, Clementine, DVDStyler, Eclipse, FileZilla, Notepad++, VirtualDub, VLC Media Player, WinSCP and more. (Other programs are available, with a little searching, or you can add your own.)
If you need to run any of these programs, all you need to do is click its Run button. Zero Install then downloads a portable version, unpacks it to a new folder so it won't interfere with existing installations, and launches it for you. Close the program later and it's entirely removed from the system.
More control is available, if you need it. A bug in the latest LibreOffice means you can't do something important? No problem, Zero Install can download and run any available earlier version, instead.
There's also support for desktop integration, which adds entries for selected programs to your Start Menu. They're still portable - downloaded and launched every time you select them - but it's easier to access them.
Zero Install doesn't support many applications, but if your favourites are on the list then it does have some advantages over building your own portable toolkit: it's easier to get started, you're always running the latest version, and optional Start Menu integration helps you find and launch your favourites.