The other day I made a post about some search engine optimization techniques for ASP.NET developers and making compliant HTML. Scott Hanselman also recently published an episode of Hanselminutes on making accessible web pages. The reason I want to point to both those resources is to bring attention to why you would want to use the title attribute in your HTML markup.
<p title="Add the title to add value to your pages.">
<a href="foobar.aspx" title="The title attribute adds extra value to links.">foobar</a>
This attribute can be added to elements, such as an anchor tag, to add description to the element. From a search engine point of view it adds value to your page and the links that help it to identify not only your page, but the destination of the link. For example if you have a link coming to your site, having a title attribute associated with that link helps identify a potential search phrase.
Browsers will typically display the title value in a tool tip as the user rolls over the link with a mouse. Screen readers will use the title to add description to the link as they read it to the user.
So as we continue the discussion about being compliant with HTML markup, consider adding the use of the title attribute to make your page more descriptive.