That depends on what kind of demon names your looking for. There are many many names from many different texts, cultures, religions. If you are just looking for anything look up a Demon encyclopedia of which there are several that you can find for free download. They also include the names of the texts from which the entity is mentioned.
If you are looking into working with a demon, trying to summon one, or looking to bargain with one I suggest you do a bit of reading from actual texts and understand what they are before you just jump in.