Several people have asked about a "good" size to aim for. 640 x 480 pixels wide is the "old" standard and ought to be viewable by pretty much any computer, no matter how old, and will be somewhere in the neighborhood of 1/2 the maximum 1 meg maximum file size requested. It should load quite quickly and still show enough detail.
I checked our Quilt Gallery section and it appears that most of the pictures there have been sized at 600 pixels wide and are certainly large enough to enjoy by all!
So, no matter what program you use to "save picture for the web", you'll do great if you size them at either:
600 pixels wide
or
8" wide with a "resolution" of 72 dpi (dots per inch)
Once you have saved your picture in this size, you should be able to attach it to a posting with a pretty quick upload time.
To actually attach a picture while posting, you need to
click on the "insert image icon" that is 3rd from the right on the bar directly above where you are typing your "Quick Reply" or "Posting a New Thread".
Then choose the Tab that says "From Computer",
click on the "Browse" button and to where you saved the resized picture and click to select it,
and the last step is to click "upload file" under where the file name will be listed.
That should take you back to your post where you should see a small "icon" of your uploaded picture.
At that point, you can continue typing or go through the same steps to add more pictures.
I hope this info helps... if you're having trouble, I'd be happy to try to help, just send me a pm.