Thx to an article in Clarín, El software ahora llevalo en el bolsillo, I discovered the world of portable apps - downloaded so many I won't be able to fit anything else in my USB drive - it's only 1gb after all!! There's plenty to go around - only a taste here. Repositories, some with their own suites and launchers.
PortableApps - has a neat Launcher, but no categories or folders are allowed.
Portable Freeware - lots and lots of stuff.
Lupo PenSuite - also has a Launcher, and plenty of apps.
The Great Geek Manual - only a section, but well organized.
PendriveApps - also with reviews.
I also found out there are many well known apps that have portable versions, or lite versions that work just the same, like Firefox & Thunderbird (and the rest of their group), Winamp, Irfanview, my beloved ATnotes, and a large etc..
There is even the possibility to boot any PC with the USB, with your own OS, according to Beginners Guides: Essential USB Memory Drive Projects & Tips. Not sure that works every time, though.