There actually is; SASS has built-in functionality that will actually inject the source filename/line-number in to the generated CSS. Additionally, Nathan Weizenbaum (one of the HAML/SASS maintainers) released a Firefox/Firebug add-on that will read this and display it in Firebug like it does for traditional CSS.
More on debug-mode: http://sass-lang.com/docs/yardoc/file.SASS_REFERENCE.html#de...
Grab the Firefox add-on here: https://addons.mozilla.org/en-US/firefox/addon/firesass-for-...