To add a Facebook share button, do this:
1. Follow this link.
2. Enter the URL you would like to share on Facebook. You can also select the button layout and size. When you're done - click Get Code.
3. Select IFrame and copy the code.
4. Paste the code anywhere on your website using the embed element.
Additional resources
Soundcloud - embed a track or a playlist
Elfsight - various website widgets
Jotfrom - contact forms
Involve.me - quizzes, surveys, calculators, forms
Infogram - infographics, online reports, interactive maps
freevisitorcounters.com / free-counters.org - free tools for counting visitors