My current cat is tiny and had her front paws declawed so I made sure to slowly introduce the dogs to her, similar to what Siu described. It took a couple weeks but they're all buds now. My previous cat was a 17lb fully clawed cat who would stick a claw in the nose of any new dog that got too aggressive. It's pretty amusing seeing a 100lb great dane/lab mix come sulking around to me with a claw sticking out of the end of his nose.
There are lots of great ideas here.. I dont know what I can add except that I had a dog and cat who started out that way and ended up *sleeping together*. Like a married couple. I'm not kidding. I have a photo. It is possible.