I just compiled a recent build of Chromium (unbranded Google Chrome) from here. I would love to start playing with extensions, so I tried stuff from there.
Alas, it doesn’t work. Since a bunch of stuff is still missing from the Linux builds, I guess extensions don’t work either.
Did anyone manage to get extensions working on Chromium Linux? Is there a flag or something to add at compilation time?

I tried it on Mac, but it didn’t work. Only Windows version allows an extension for now.
I’ve found a dirty little workaround for this issue and felt obligated to share it.
I don’t know if you’re dual-booting, or have access to a Windoze box, but if you take the folder with the long extension ID from a Windows Chrome install:
C:\Users\”your user name”\AppData\Local\Google\Chrome\User Data\Default\Extensions
and paste it into the corresponding folder in your linux install:
/home/”your user name”/.config/chromium/Default/Extensions
then start chromium-browser with the –extensions-enabled flag, it ‘just worked’ for me. Once you’ve restarted Chromium with the flag, go to chrome://extensions/ to verify that it worked.
It seems that they’ve started building auto-install support into the linux port, but the furthest it got on my system was creating a TEMP folder in the Extensions directory when I downloaded the .crx file and copied it there, in addition to downloading it to the Downloads folder. It just doesn’t unpack the .crx into a usable extension. I found a python script to package an extension into an installable .crx, but haven’t looked into unpacking it at all. That’d be loads better than relying on a Windoze install of Chrome for your extensions.
Good luck, and let me know how that went!
This is actually a moot point now, as it seems that extension installation is fully supported in the most recent version of Chromium in the PPAs.
Good to hear!
This tutorial might help
http://jaxov.com/2009/09/install-chromium-extensions-plugins-in-ubuntu-linux/
I tried this tutorial and it worked for me…
http://jaxov.com/2009/09/how-to-install-google-chrome-chromium-extensions-plugins-in-ubuntu-linux/