I don't know if it is the easiest but, if you are using Windows, FastStone's Image Viewer offers a LOT of bang for the buck. While it is freeware, the developer asks for donations. It will resize and compress your digital files, although you cannot (unlike LR3 or PSCS5) directly dial in the final file size. This is not a problem since the final file size is updated in real-time as you adjust the image size so you can readjust the image size until you get below the 100K limit imposed at WC.
FastStone's image viewer/browser (one of the fastest around) also has quite a lot of editing capability and has become more robust with each new version. It now offers local editing, cloning and healing along with a lot of global adjustments like colors, levels, curves, sharpening etc. plus some auto adjustments. It has got to be one of the best software bargains out there. While I use other editing/browsing tools (ViewNX2, NX2, LR3, PS), I keep this gem on my computer because it can do other stuff that I haven't mentioned here. Hope this helps.