United Airlines announced they will be flying from Newark International Airport to Porto on a daily basis. There are direct flights in some cases, but 1 stop is even more reasonably priced. The good news is that you will NOT have to fly through Lisbon. The one stop can be in a variety of European cities and Lisbon can be avoided altogether. Anyone that's used LIS as a connecting city knows it is not the most user-friendly airports, especially the badly over-crowded passport control/customs area. The fares right now are insanely good and I was able to find a one-stop each way round trip from Newark to Porto for under $560.
Yep, that is a crazy good deal, even for some of us on the west coast. Grab your tix soon and save tons of money. That's about half price on a major air carrier.
Oh yeah, now I am reminded of the strike that was going on the last time I went through Lisbon, and how long it took to get through passport control. I was late to get to my plane, but so was everyone else, so the flights themselves were delayed. Luckily I had plenty of buffer for my subsequent connection.
If you're using Lisbon as a stop-over to get to Porto, consider doing the Lisbon-Porto leg by train. 1st class tickets costs €20-30 if bought in advance and the journey does take 2½-3 hours but it drops you off either in Vila Nova de Gaia or at Porto Campanha, but it saves a load of hassle using the air bridge with the different baggage allowance on that tiny plane.
The train is very reasonable and pleasant. I've taken it before. On my recent trip I flew into Porto via London, but out via Lisbon. That's what was cheapest.
Rail sounds like a fun option.
I looked at tickets on http://www.raileurope-world.com. What's the deal with reserving a train? I get the impression that you buy tickets that are good for a 4 date range, but you then need to reserve the actual date/time you want in order to guarantee a seat. And something about reservations only being available locally.
You can buy tickets up to 60 days out. Prices Lisbon<->Porto are in the 30-40 range, but there are some as low as 22 if you are buying enough in advance.