I love FireShot but it's windows only, I do see that it comes for Chrome as well but still Windows only. Anyone found anything for Chrome on Ubuntu?
Related but still FireFox: Is there an equivalent to FireShot for Firefox?
There are a fair few "Screenshot" extensions for Chrome.
As you said, there is FireShot: Quick Captures and Annotations but that is Windows only.
Another alternative I have found Awesome Screenshot: Capture & Annotate extension which seems to have reasonably high ratings and have similar functions.
FireShot's Chrome page states the following.
Their website posted this comment which unquestionably says that there will be no Linux support.
There is famous screengrab. You have to patch the install.rdf file in sreengrab's xpi, which is a zip, as described here.
This works fine for Firefox 8 on Ubuntu 11 and even on Windows 7. As compared with Firefox version 3.x (once screengrab had been developed for those versions and then stopped for some inexplicable reasons.
I tried to get its source code, however impossible so far) the only difference is that the screengrab icon won't appear in status bar after having been patched and installed. So you might make use of right mouse button to carry out any screengrab function.