Is there a site out there that shows 'hardware charts' made by Linux users?

And here's a specific request: Which external hard disk drive (USB connection) would you recommend?

I'm looking for one with these attributes (in order of importance):
- compatible with my current Linux distrobution (Ubuntu) on the laptop
- large capacity (at least 500 GB)
- fast (but still reliable), quiet!
- physically small (ideally abouit 7x4x1 inches) and light-weight
- low energy consumption (ideally, so it can be powered by USB)
- fairly cheap (or rather: as much GB/$ as possible)
- design can be ugly

It's primarily going to be used as a storage/backup device for my home directory. But I would also like to share files from it with friends, so it needs to be accessible for systems with Windows XP/Vista. Which filesystem should I use?

The LQ Hardware Cmpatibility List may be what you are after. Individual distros have their own. Another way of doing it is to plug the model you are after buying into a search engine and put Linux at the end of the search and you can see if there are any problems.

Generally speaking, a USB drive shouldn't give too many problems unless the manufacturer insist on the drive having a software setup with their own software provided.

1. Compatible with Ubuntu. Well, it is rather hard to design USB storage that would work without driver installation in XP, but not in Linux. And being Windows-usable without installation of a load of spyware is an expectable drive property, so you can check it when you have nearly decided everything.
2,4,5. USB-powered and being lightweight means 2.5" disk. 500GB means 3.5".
3.Fast means high-RPM 3.5"... Quiet means 2.5". And reliability is hard to tell for new models.. If I would want maximum reliability, I'd buy separately an USB enclosure and a 500GB HDD which is being phased out but still is not synonym to failure in Internet. In case of IDE, better test that USB enclosure supports anything above 127 binary GB.
6,7. I feel like spending some effort and buying separately an enclosure and a drive will yield better results.

About FS - if you want a sane native Linux FS which is at least readable from Windows, go with ext3 (and ext2 read driver whenever ext3 read driver is unavailable, I can't say what is current compatibility situation). For Vista leave a small FAT32 partition.