I'm a little late but in case you are still looking, I have really liked Truphone. The per minute usage cost is a little high but it is perfect for the very occasional user as your prepaid credit NEVER expires. Plus, it works in a number of countries around the world.
I live in Canada and travel to the US 1-2 times a month for short trips. I also go for weekend trips and 1-2 week vacations a few times a year. I was looking for a SIM that would give me small amounts of data (just to look up stuff, use Google maps, etc) and a few mins of talk and text (to text each other if necessary and to call local businesses when necessary - generally for restaurant reservations lol). I mostly use wifi for everything else.
You buy a SIM for $30 and you get a free $15 credit. It is 9cents a min outgoing, free incoming, 9cents a text and 9 cents a MB. A little pricey, but I generally spend about $10-15 total a year. One time I was on a 1 week trip and spent maybe 45 cents total making a couple of restaurant reservations and looking up something quickly. Their main website defaults to their business plans so you have to do a little extra searching to find their consumer site:
https://www.truphone.com/us/consumer/sim/Their customer service is superb (although I haven't had to call for 2+ years now). The first 1-2 years I had to call several times for a variety of reasons and I was thoroughly impressed. Agents in a call centre in the Philippines who were polite, spoke great English, and went the extra mile to be as helpful as possible. I was fully expecting your typical crappy cellphone customer service and was blown away.
If I am going somewhere for a long time where I need a lot of data, I just buy a $20-30 monthly prepaid SIM. Which is cheaper when you are using several GB of data.