You can resize upon export in iPhoto. That aside, I think you're right to look for something else, as iPhoto isn't a great bit of software.
You can also resize in Preview - it's a surprisingly competent bit of software in fact, considering it's free.
If you choose to get into photo editing a little deeper, then I'd recommend looking at Pixelmator. It's not free but good value for the money.
http://www.pixelmator.com/mac/