There are numerous brilliant tours on Roundme which are public and really worth to be shared.
To share the tour you browse:
1) Open the tour;
2) If you are the author of the tour, switch it to the View mode;
3) Click the 'More functions' button and choose 'Share & Embed' option:
4) There are different share options available, click to choose the one you need (You can use your Facebook/Twitter/Google+ account to share the tour, or you can simply copy the direct link to the tour)
Every Roundme tour could be also easily embedded to the web page or application.
You can learn more about the embed options here.