Yeah, wxwax is corrrect. The reason digital cameras have so many pixels is for printing, where you can really see the difference between a pic with lots of pixels and one with few. And you can generally compress the image much harder (in Photoshop, jpg compression 5 is usually okay for online display) without being able to see much difference.
There are online sites like pbase & smugmug that don't make you go through all that. You just upload your pics and a gallery automagically gets made with original sizes retained for printing and a choice of smaller photos for online display, compressed and sharpened at reasonable settings for small file sizes but good quality. You can link to ADVrider from both those services to display your photos in posts.
Disclaimer: I work for one of those companies but you should feel free to use any you wish, including some others out there like ofoto.