We are going to Barcelona in May to catch a cruise then afterwards our friends from UK that are meeting us on the cruise have asked that we come stay with them.

Airfare has gone WAY up since we first looked and I need help figuring out how to get the best deal. I've spent days searching.

Anyone have any tips?

We usually fly Bristish airwaysin May and for the last several years they have had a sale which starts around mid February. It is usually only a 3 day sale so you have to keep checking.
You may want to sign up with them to get e-mails on promotions.
I'm hoping to purchase our tickets then.

Have you already purchased your Barcelona ticket, and are just looking for a Barcelona-UK-Barcelona fare? If so, log onto the Iberia website as a Spanish website and monitor their fares from Spain. They could be a lot cheaper than a fare purchased from US. You'll have to take the risk of buying while in Spain, but I didn't have any trouble doing so last year and got a much better one-way fare than if I'd purchased in advance from North America. You could also check to see which discount carriers fly from London to Barcelona, and buy one way fares Barcelona-London-Barcelona.

If you need a US-Barcelona-London-US fare, telephone British Airways (and maybe BMI - not sure if they do this) and ask about a "Europe pass" type ticket. You can sometimes get quite cheap fares for the UK-Barcelona-UK portion of the trip (cheaper than what you'd see if you looked online). Also, connecting through the UK (rather than flying directly to Barcelona) might result in a cheaper fare on the trans-atlantic portion because of the hassle of the connection - but in this case it gives you the stopover you need.

I misssed a great airfare also last weekend...400 to europe from boston. They all seem to be up there. I wanted to fly into london and return from rome. the prices are very high. Has anyone used that europe by air?

Take a look at:

http://www.whichbudget.com/

I'm not entirely sure what European route you intend to fly, but if it's between London and Barcelona, try easyJet. They usually have excellent fares, albeit with no-frills service, and they fly to BCN, Barcelona's main airport. You could also use RyanAir, but the airports they use to serve Barcelona -- Girona and Reus -- are actually an hours drive away.