ImageXY is an image resizer for OS X, available for 10 dollars on the App Store.
That’s quite a lot for something simple like an image resizer, and some people will baulk at spending that kind on money on third party software when Preview (which comes built in to OS X) can do the same job.
Preview can do the job, but ImageXY is a specialist tool and worth considering if you spend a lot of time messing about in Preview to get images to the right size.
For starters, it’s blazing fast and completely painless, handles images dragged in from almost anywhere, and doesn’t complain if you drag in hundreds or even thousands of them. It comes with a small selection of resize presets (640px wide for blog post pics, 128px wide for profile pictures, and so on), but you can add your own presets too.
You can drag in images from almost anywhere. Not just Finder, but iPhoto, or your web browser, or Mail or whatever. Not just images, but folders full of them if you like.
Did I mention how blazing fast it is? When you’re talking folders of 100s of images, it doesn’t even break a sweat.
OK, at $10 it’s not the cheapest option for image resizing. As I said above, if you rarely resize anything, just use Preview; and if you know how, make an Automator workflow (a different one for every output preset you want). But if you just want to save yourself time and hassle, and do a lot of image resizing on a daily basis, ImageXY will probably be 10 dollars well spent.