So, you want to run Chrome (or Chromium), but you're annoyed by the lack of client certificate authentication on Linux. Turns out, this is relatively easy to solve, there's just no UI for it as of yet. (As of 11/13/2009.) (Note: I'm doing this running the daily build from the chromium-daily ppa on Launchpad - if you're running Debian or Ubuntu, you can add "deb http://ppa.launchpad.net/chromium-daily/ppa/ubuntu karmic main" to your /etc/apt/sources.list if you want to run this. It may work on the official Google build as well, I'm not sure.)
You want to use the instructions at
Google's page on LinuxCertManagement to install the MIT CA. You may also want the CSAIL CA (specifically, the Master CA). If you're
running Debian or Ubuntu, the short version of that LinuxCertManagement page is
to install libnss3-tools, then run "certutil -d sql:$HOME/.pki/nssdb -A -t
Recent Linux builds should be able to generate certificates via the usual web interface, however there will be no UI feedback in doing so. Failing that, the easiest way to install a client cert in the nss database is simply to install it on Firefox; at that point, it should be in the list of certificates you get when you run "certutil -d sql:$HOME/.pki/nssdb -L". If not, go back to the LinuxCertManagement page and do it manually.
Here's the last key to the puzzle: Chrome on Linux currently lacks a UI for selecting a certificate, so run it with the --auto-ssl-client-auth flag. Enabling this flag configures Chrome to automatically send an certificate to websites without prompting, as Firefox will do under certain configurations. This is considered a privacy issue; see UI notes #3 in the Chromium design document and the linked Mozilla bug. Bug #25241 tracks this issue in Chrome on Linux.
You'll probably want to edit both Preferred Applications and the Main Menu entry (I'm assuming you run Gnome here; if not, there may be other things you want to edit) to reflect this, so links you click on outside of Chrome open this way. (Gnome Do and similar pull their data from Main Menu, among other places.) Once you've done this, you can check your work with this demo page. If everything is working, it should welcome you by name, and tell you that a certificate for your username is installed.