Question: All of the ones I can think of are specific products that have come to represent their kind. This is usually either because it is the first of its kind, as in a Xerox machine (the first office photocopier), or it arises from popularity, as in Sharpie or something like "Google that" (though I'd say that's a bit informal/debatable).

Other examples I can think of off the top of my head are:

* Kleenex
* Post-it

Answer: 
What you are looking for is called a [*genericized trademark*, *generic trademark*, or *proprietary eponym*](http://en.wikipedia.org/wiki/Genericized_trademark), and Wikipedia has a huge list:

* [List of generic and genericized trademarks](http://en.wikipedia.org/wiki/List_of_generic_and_genericized_trademarks)

It includes all the examples mentioned by chaos and yourself, and many more.

See also this related question:

* [What is a word/phrase for using a term for a popular special case instead of a generic term?](https://english.stackexchange.com/questions/7235/what-is-a-word-phrase-for-using-a-term-for-a-popular-special-case-instead-of-a-ge)
* iPod (I've seen many people use iPod to refer to any MP3 player)
* Xerox
* Zip-lock