I realize that a lot of people have been posting about that wondermachine thing, but I thought this was interesting that on Samsung's own FAQ they give you the tools and a step-by-step to easily sideload Apps on the captivate without rooting the phone. I just did it on my phone a moment ago and it was very quick and painless.
Link for anyone who is interested:
How Do I Side Load Applications On My SGH-i897 (Captivate) Phone Using The Android Debugging Bridge (ADB)?
Link for anyone who is interested:
How Do I Side Load Applications On My SGH-i897 (Captivate) Phone Using The Android Debugging Bridge (ADB)?