Jez just emailed:
Now that I´ve made the switch to Firefox (on Linux, too!), I´m *really* starting to get annoyed by all the websites which open links in new browser windows, rather than new tabs.
To enable it - browse to "about:config" and scroll down to browser.tabs.showSingleWindowModePrefs - this is false by default, double click to set it to true.
Now, if you go to Tools -> Options -> Advanced, under the "Tabbed Browsing" section, there will be a checkbox entitled "Force links that open new windows to open in: ", and you can either select for them to open in the same tab or a new tab. Hurrah!
Hope this relieves you of your annoyances. Maybe I should blog it...