I certainly don't know the answer to the colour problem but it's worth remembering that most online galleries - PrestoPhoto and Flickr for sure - convert (if required) all images to the sRGB color space, so if you've been working in AdobeRGB it can look different. PrestoPhoto also increases the size for the 'large' version and that wouldn't help.
Your web browser (unless you use Firefox with a color management add-on) will display only sRGB. (Having said that about Firefox, I've tried to test this with two identical images, one in sRGB and one in AdobeRGB and still can't tell the difference).
Have you tried viewing your images online anywhere else, like Flickr or some other gallery? Is there a difference? If there is then maybe PrestoPhoto is doing something odd.
Without calibration tools, though, try to just upload a few pictures to an online gallery, then get as many people as possible to view it. If the majority find no problem with it, then the image must be ok, no? If a small minority have a problem then the chances are it's their monitor problem and not yours.
Looking through your gallery, I don't see a problem, though it's possible that some of them are very slightly pale.