Getting around Paris, London, Rome

kayak.com is a good site for researching flight prices. Use the multi-city options to search for flights into one city and home from another. I would suggest that you fly into London and home from Rome (or vice-versa). From London to Paris, the train called the Eurostar is the most convenient, but you may have missed the cheapest prices. From Paris to Rome, you may want to fly.

For London this summer, there's a small event called the Summer Olympics there. Might be a bit tough to get hotels. Great inexpensive transporation into the city but if you take the underground, you may encounter a lot of stairs with your luggage. Rome and Paris are equally as easy to transport to the center of the City. For Paris, you again encounter the stairs if your take the cheaper RER train and metro. Taxis are expensive. As for which is cheaper to fly into and out of, you'll need to do your homework. I would suggest flying into one city and flying out of another.

Actually played around with this about two weeks ago and at that time, from Seattle, the best deals seemed to be into Paris. I was checking: LHR, Athens, Frankfort and Paris.