Top 20 Stealth Links

In another thread on Virtual Page Rank [webmasterworld.com], we talked about ways that you can link to a site other than a direct http href link or links that may not show up on the link command radar.
Lets start a list of the ways sites can link, refer, or point urls to your pages other than direct hrefs. Mainly, we are after ways that SE's such as Google may run into and use urls they find:

another site links to your graphics ( img src=http://www.searchengineworld.com/gfx/logo.png )
a site links to your javascript files
a site links to your css files?
rss feeds and other xml feeds that people can link to without notice or referrals necc being generated.
links in email that some se's can read (yahoo mail, hotmail, Gmail [webmasterworld.com])
links marked with noindex
links marked with nofollow
raw urls within javascript or js comments
raw urls within css or in css comments
urls within meta data of graphics and video files
urls within html comments
urls within the head section, meta data of a html page, or alternate html entities (alt, name, id, etc)
links or pages that maybe surfed while visitor has page rank engaged on the toolbar
the target of a constructed, obfuscated, or encrypted js url (hidden until executed)
links behind pay walls that Google can spider via webmaster tools
Domains that have been 301'd with links.
Links in Flash movies (games, quizzes, etc).
non href'ed url's. (raw url on page http://www.webmasterworld.com)
Links in any documents other than web pages e.g. .doc, .pdf, .txt, etc.
blocking a page in robots.txt should make it blocked from bots, but they still spider it.
Domain registrations/Whois and DNS data
Links in form data.
Links in other Google produced software (gadgets, widgets)
NonTraditional pages (irc, twitter, UseNet, Yahoo, or Google Groups.
Advertising links (AdWords/Yahoo), and other services like Maps.