Xerox has come to be a word in English through sheer market strength of the company bearing its name. Even though the company doesn't dominate the copier business anymore, I think the word will remain for a while. Other words that come from brand names:
[ul][li]Magic Marker - This company actually went out of business several years ago, but I still use the word to describe permanent markers such a Sharpie (The heir apparent that might misplace the 'word' Magic Marker)[/li]
[li]Palm - As in Palm Pilot. People often refer to PDAs in general as 'Palm's[/li]
[li]Q-Tip - Perhaps the best example - in the US, anyway.[/li]
[li]Hoover - Especially used in the UK (from my admittedly limited American knowledge)[/li][/ul]
I don't think Kodak has ever quite achieved the same status. I wouldn't us Kodak as a verb, but I have heard others do it.
I think this could be a lengthy thread unto itself.
John