Another tip for the bookmarking sites: You can add “&tags=XXX” to the URL to automatically enter in some tags on the posting page. Just replace XXX with whatever tags you want. Diigo separates by comma, Delicious by space (you might have to put “%20″ instead of a space, I’m not sure).
If your favorite bookmarking site isn’t here, rolling your own for your favorite site is easy. Just check out the API & bookmarklet for your site, and refer to the above examples as a reference. I’ve never worked with an API before, but figured out diigo’s in a few minutes.