Honestly, it was way easier for me to just change the picture size default setting on my camera instead of having to resize every photo in a program. Most digital cameras have the option now. Typical setting are 1600x1200, 1024x768, 640x480, and "postcard". The 640x480 setting works perfectly for me. Not having to resize every photo you take makes it so much easier.
I would take my camera and take some pictures with a few different size settings and then see which sizes upload without being over-limit. Then use that size as the default for taking pictures.
...Of course if you do not have this option with your camera I apologize for wasting your time.