Adblock-like plugin for hiding social sites' widgets, buttons, etc
Solution 1:
The Fanboy Annoyance Block List for AdBlock Plus in Opera, Firefox and Chrome:
Blocks Social Media Content, In page Pop-Ups and other annoyances; thereby substantially decreasing web page loading times and uncluttering them.
Solution 2:
Ghostery does that; works with all major browsers.
Also, the "Antisocial" subscription for AdblockPlus.
Solution 3:
For Firefox, I use the Greasemonkey add-on and the Remove Facebook Like buttons (mod1) script.