Oh I feel for you Vettecor...
A few years ago, I took in a stray, who promptly gave fleas to my two kitties. I used Capstar, as doodlebug suggested, to get rid of the immediate fleas. Then I used Revolution, which one of my kitties had an adverse reaction to, even though it's considered extremely safe.
It took weeks of constant vaccuming to get rid of all of the fleas, but for weeks afterwards, I was convinced that they were still around. I called the exterminator in February. She thought I was out of my mind, lol. The mere thought or mention of fleas makes me itchy. Ugh.
Do make sure to vacuum very thoroughly, along baseboards, by windowsills, and every upholstered surface, on every inch of couch, using a crevice tool and brush, and wash anything that's washable, including curtains (or vacuum, especially along the bottoms).
Once I was pretty sure that the fleas were gone, I dusted some diatomaceous earth into kitty beds, the loveseat, and the living room area rug, as those were the places where my kitties spent the most time. Left that all for 24 hours then vacuumed it up.
I hope never ever to have to deal with those nasty little things again.