@ wasp
You could also combine hiccup's suggestion with the existing web links function (as seen in phred's post re:Wikipedia / Google links)
You could activate one of the built-in custom WWW tags, add your link and use
You could add Track information (2) to your layout and have it displaying the comment tag.
And then in the standard information panel you could add something like:
$IsNull(<Comment>,,"notes present")
That will alert you when a song has notes added.
Just changing the Comment tag for
$IsNull(<WWW>,,"links present")
and displaying the links at the bottom of Track information (2).
There is a drawback in that the links are always displayed in Track information (2)
They are just dimmed if the links aren't active.