Facebook has two methods of sharing. The “Sharer” link is simple but the preferred Facebook way is using the Share Dialog. This method does require an app id but offers more flexibility.
Sharer:
https://www.facebook.com/sharer.php?u={url}
Share Dialog:
https://www.facebook.com/dialog/share?app_id={app_id}&display=page&href={url}&redirect_uri={redirect_url}
https://twitter.com/intent/tweet?url={url}&text={title}&via={via}&hashtags={hashtags}
Google+
https://plus.google.com/share?url={url}
https://pinterest.com/pin/create/bookmarklet/?media={img}&url={url}&is_video={is_video}&description={title}
https://www.linkedin.com/shareArticle?url={url}&title={title}
Buffer
https://buffer.com/add?text={title}&url={url}
Digg
http://digg.com/submit?url={url}&title={title}
Tumblr
https://www.tumblr.com/widgets/share/tool?canonicalUrl={url}&title={title}&caption={desc}
https://reddit.com/submit?url={url}&title={title}
StumbleUpon
http://www.stumbleupon.com/submit?url={url}&title={title}
Delicious
https://delicious.com/save?v=5&provider={provider}&noui&jump=close&url={url}&title={title}