Thanks for these replies.
To clarify, I am meeting exclusively with software companies, and from what I've learned there is apparently a trend amongst software companies to be more casually dressed than banks or government agencies. And, it seems that the larger the company is, the more formal the dress is. Smaller tech companies like startups with, say, 15 people seem to be pretty casual with a short sleeve collared shirt and nice trousers the norm.
Jeans, apparently, and not worn in many business situations at all.
I have a couple of meetings with medium size companies, i.e. 100 people. So, for those I'm thinking that a long sleeve collar and tie would do the trick, and for the smaller/hipper/techie companies maybe a nice untucked collared shirt would be fine. I picked up a couple of pairs of nice tropical wool style dress pants that should work for either.