i've been having fun with .dsl extensions. this should probably only be done with cloud mode, and even then it's not a good idea.
but if you don't care about disabling wget or awk and thus appbrowser and who knows what other parts of tc, it is pretty trivial to "install" .dsl and .tar.gz extensions from dsl.
some work easily, others not so much. the ones i'm listing are from the "testing" category.
jb4x4's wine-0.9.28_with_opengl.dsl: this allowed me to install and run notepad++. i don't use notepad++ but it indicates i can do some things with wine until robc creates his wine extension for tc. by the way, i had to mount an external drive because even though i had enough free space to install notepad++, the installer was unable to tell and refused to without telling. there is a .zip but then you'll need to install zip.tce.
florian's flwm.dsl: this was fun. had to install libstdc i think, plus had to edit /home/tc/.xsession
nickelplated's flock-0.7.1.tar.gz: if you run getflash and sudo mv /usr/local/firefox/plugins/*fl* /home/dsl/flock/plugins that should let you use youtube in flock. why you'd want to only you could guess. you probably need minefield working first.
curaga's gifsicle.dsl: text2gif -t " created with " > 1.gif
text2gif -t " tinycore linux " > 2.gif
gifsicle --delay 100 1.gif --append 2.gif --loopcount > anim.gif
sometimes you just can't get the libs needed to run a .dsl extension, other times you can either by installing a program with similar needs (minefield) or installing the lib from appbrowser.
the most useful application i've run this way is inkscape from the applications category. but you do this at the cost of a tc session where you know what's going on, you guess that you have the right deps by running the app, and even if you have them all and don't disable something important like wget or gtk2 (in a way that it won't reinstall,) you're still running something compiled for another kernel. not a real solution, certainly not a great one.