You should be able to find some in the kitchen (sorry, bad joke)

I don't know any other by name but if there are they should be listed under "Houselfs" (The wiki page)

There are definitely a lot more elves though

Those are all the named ones.

...Besides, you're saying it wrong. It's 'House-elf' not 'House Elves'

-Hermione Granger

House Elf is singular, House Elves is plural.