We have our JFBCSocialShare module, which lets you add multiple buttons to a page, like in the bottom right of this site. Unfortunately, the JomSocial social stream doesn't allow Javascript to be executed when the page is loaded, which means there are some big limitations on what we can do.. and a popup would be very difficult to do with those limitations.
The way the FB Share button works is to use an iFrame to Facebook's site. Facebook has an option to use an iFrame, but not all social networks do. Many only allow Javascript tags which, as mentioned above, can't be done in the JomSocial stream as far as I can tell.
If you need assistance with other buttons like the Share button we can probably help with some to add the iFrame version of buttons that offer that option. Let us know what buttons you specifically want and we can look into if it's possible or not.
Thanks,
Alex