There is no less than 3 different versions of Chrome available in Ubuntu. None is available in the official Karmic repositories but the browser you want is just a PPA away.
The safest bet is to use the Google Chrome PPA. It's maintained by Google itself and that's where the official version of Chrome for Linux are. If you install Chrome from the Google website, you'll get the google-chrome-beta version from this repository.
The second option is google-chrome-unstable. It also comes from the Google repository, it's just a little bit more bleeding edge.
And the 3rd one, for those feeling really brave, there is a PPA with the Chromium builds: it's called Ubuntu Chromium Daily Builds and the package you need to install from this repository is chromium-browser. Now, this one is not for the faint of heart as this package is built entirely automatically and does not get tested at all. It's generally ahead of google-chrome-unstable by a few days.
Still undecided? You can compare all 3 versions on the chrome(*) page. It's updated daily, list all the available version and links to the PPA pages for installation instructions.
Here is a snapshot of the 3 packages taken on Feb 24th:
And finally, good news, in Lucid (soon to be added to ubuntuupdates.org), chromium-browser is in the universe repository, no need for a PPA anymore.
