Here's a collection of linking related tid bits you should be aware of.

Paying for a link at Overture.com (formerly GoTo.com) that is not in the top five in the search results is, in most cases, a waste. Results of six and lower are not made available to the Overture partner sites, which collectively have millions more users than Overture does alone. Like AOL, for example. If the cost increase is just a few cents, get in the top five, and your site could be found across all of Overture's partner sites rather than only at Overture.com
http://www.overture.com

Did you know that search result links from Inktomi can vary from partner to partner. In other words, obtaining a high ranking through Inktomi will become harder over time since the partner site can tweak Inktomi results.

Have you ever noticed how some sites have multiple links at Yahoo! even though Yahoo! plainly states that the most they will give a site is two? Yahoo! definitely shows favored nation status to certain sites. Do a search at http://www.yahoo.com for the term "Discovery School" and you'll see what I mean.

If you want a cheap way to track visits to your site that are generated via links embedded in email messages, just create a duplicate page/URL that is marketed only via email. Nearly all visits to it would have to come via email clicks on it. The only exception is if someone links to that URL or bookmarks it.

The Netscape Open Directory, which started as NewHoo several years ago and then became DMOZ, wasn't taken seriously at first by most folks. Fast forward a few years: It now is as powerful as Yahoo! and LookSmart, distributes listings to more than 300 other sites, and offers multiple link opportunities to your site
(if your content truly justifies it). BTW I'm a category editor at Netscape
http://directory.netscape.com/Computers/Internet/WWW/Best_of_the_Web/Web_Reviews/
So if you publish web site reviews on your site let me know.

In some cases, you can purge a dead link from a search engine by submitting that same link/URL to the engine where it's appearing. But before you do so you might consider re-creating the dead file, since the search engine thinks it's still alive.

Overture isn't the only pay-per-click search engine worth utilizing. About.com has its own auction based search service called Sprinks, and I like it.
http://sprinks.about.com/

Want to scare yourself? Read "The Link Controversy Page."
http://www.jura.uni-tuebingen.de/~s-bes1/lcp.html

How long will it be until someone takes what LinkPopularity.com does and makes a business out of it? How long will it be until search engines charge for this info? And when they do, I hope they'll be able to answer questions such as, "What sites are linked to my competitors' sites but not to mine?" or "What links to my site and my competitors' sites have appeared within the last week?" I'd pay to subscribe to such a service.
http://www.linkpopularity.com/

Do you know what link equity is? Link equity is all the work you've done to build links to your site, and the links themselves. Did you know that many failing dot-com sites sell their link equity to competing sites. If you have a bunch of links on other sites pointing to your site, before you close your doors, contact your competitor and offer your domain, and it's link equity to them. The harder part is valuation of links. A Yahoo! link is more valuable than a link from your Geocities page :)