I had the question posed - do you HAVE to sharpen and resize for the web? The simple answer is "No". However, if you want your photos to look their best, you SHOULD sharpen before resizing for the web. Why? Because, in the process of resizing (or dropping the resolution from, say, 300 ppi to 72 ppi) for the web, the photo often gets blurry and/or soft. That's not how you want your awesome photo to look after your love and care in processing it!
Now, the amount of sharpening can vary. In Scott Kelby's book "The Photoshop CS2 Book for digital photographers" he uses Unsharp Mask to sharpen before he resizes for the web, and the amounts he uses are "Amount: 400%, Radius: 0.3, and Threshold: 0. Now - I find that a little overdone, but it's really a matter of what you think looks best.
But, for saving for the web, this is how I do it using Photoshop Elements 5.0 (if I were using Photoshop full version - I would do these steps using the Lab Color Sharpening technique found HERE)
1. Open the photo you will be resizing for the web. Do all the editing you want to do - sharpening is ALWAYS the last step before saving. ALWAYS PEOPLE! LOL! OKay, when you are ready to sharpen, click Enhance>UnsharpMask. If it's not there (depending on your version), you can also find it under File>Sharpen>Unsharp Mask. It's all the same thing. When the screen pops up, I enter these values:
If you can't see them well enough on here, it's Amount: 120%, Radius 1.0, and Threshold 3. You can always increase the amount and decrease the Threshold to your liking, but these are the numbers I use.
THEN, I click OK.
2. Now - RUN THE SAME STEP AGAIN. Yep - I do it twice. Twice is twice as nice :) That's the sharpening I do before saving for the web.
If you have your own way of saving for the web - great! Do it that way. Whatever works. I happen to use the Save For Web function in Photoshop because it's easy and precise. I love it. Okay, here's what you do.
3. Click File>Save for Web
4. Depending on the size of your image, you may have this little screen pop up - just click YES.
5. It might take a minute to load, but this screen will pop up. Your image will be so big that you won't even be able to see all of it on the screen. What we are going to be changing is these values:
6. Most sites want your images to be about 600 pixels wide/high. Mine is a horizontal image, so I'll enter 600 pixels for Width, and as long as your "Constrain proportions" box is checked, the Height will automatically adjust as well. Then, change the quality to about 50% or so. Click "Apply" (the box right below the "Constrain Proportions" box).
7. Now you'll see your image as it's been resized for the web! All you do now, is click OK - rename and save it where you'd like. The default location is usually in "My Pictures" or whatever equivalent.
Here are the results: