I did a grep for urls in docstrings which might be hyperlinked.
Diff below from the lisp directory.

It'd be tempting to have M-x checkdoc report on this sort of
thing, except it may too often hit sample input etc instead of
actual followable links.


2009-07-16  Kevin Ryde  <user42@zip.com.au>

	* erc/erc.el (erc-cmd-MODE): 
	* mh-e/mh-junk.el (mh-spamassassin-blacklist,
	mh-bogofilter-blacklist, mh-spamprobe-blacklist): 
	* net/newst-backend.el (newsticker--parse-atom-1.0,
	newsticker--parse-rss-0.91, newsticker--parse-rss-0.92,
	newsticker--parse-rss-1.0):
	* progmodes/idlwave.el (idlwave-mode): 
	* progmodes/idlw-shell.el (idlwave-shell-mode): 
	* progmodes/vera-mode.el (vera-mode): 
	* progmodes/verilog-mode.el (verilog-auto-inst, verilog-auto): 
	* progmodes/vhdl-mode.el (vhdl-mode): 
	* textmodes/table.el (table-generate-source)
	(table--warn-incompatibility): 
	Hyperlink urls in docstrings with URL `...'.