BuddyPress.org

Do not use widgets that make use of iframe or script tags in a loop! Very bad load performance like you said!
Unfortunately you cannot use something like FB Like without an iframe or script tag as it requires pinging FB for the like count.

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Whenever possible, use links instead. The Shareholic API can help:
http://www.shareaholic.com/api/

There are probably other similar APIs out there as well.