So I've been using a Mac for a few months now and am pretty much acting like the slowest kid in the class on the first day of school when it comes to using it.
One thing I am kinda bugged by is how everyone suggests using Photoshop for even the simplest of stuff... such as quickly resizing pictures (You know... 6mb pictures of kittens that your grandma sends you directly from her digital camera). I tried all sorts of 3rd party apps but each one of them came with their problems.
Then today I realized one simple thing.
Just open the picture in Preview and click on Tools-> Adjust Size.