I recently launched a computer price comparison site
called Compare Components. Linux hardware compatibility is one of the search options so you can find hardware (like wifi cards) filtered by linux compatibility, location, manufacturer, etc. Price comparison is possible across international borders (currently focuses on the UK, US and Canada), and it will automatically calculate relevant taxes and charges in your native currency.
The system is still under development but is stable enough for day to day use and I am keen to promote it. If anybody has any ideas for improvements or ways to market it (without spending money), then I would love to hear them so please comment on this journal entry.