• Open the image and rotate it as necessary
• Resize the image
  • Click Image→Image Size…
  • Enter a width of 500 pixels, the height should change automatically.
  • Click OK
• Save for Web
  • File→Save for web…
  • Choose JPEG and Maximum from the dropdown options.
  • Click OK and save the new image in a place where you can easily retrieve it for uploading.

If you can't get your hands on a copy of photoshop, this software can stand-in for most uses and it's free… http://gimp-win.sourceforge.net/stable.html

• Open the image and rotate it as necessary
• Resize the Image
  • Image→Scale Image…
  • Enter a width of 500 pixels
  • Click Scale, the height should change automatically.
• Save the Image
  • File→Save As…
  • Rename the file appropriately
  • Expand Select File Type (By Extension)
  • Select JPEG image
  • Click Save
  • Check the box Show Preview in image window
  • Move the slider to the desired quality (I like 95 or better)
  • Click OK

Here's another one that should be pretty simple to setup and it's free to download and use. I have not tried resizing/optimizing for the web with this one but it should be pretty easy. Directions forthcoming… http://www.irfanview.com/