Now that google has anounced their new Google trends site I couldn't help but mention it. If you spend any type of money at all on SEM you need to check your keywords against this site.
There are a couple of intro articles about the new service at Micro Persuasion and TechCrunch.
To get a real feel for how important this information will be you should try out a few queries for yourself. Take a simple query like "motorcycle" and then look at the regions tab. A lot of the queries about motorcycles originated from the Philippines. Now look at "pizza", most of the queries there originated from the US. That should make it much easier to target your audience with your advertisments. The trending is nice as well and should give marketers a better idea of when to boost spending to maximize exposure.
This follows another tool Google just release for their AdWords service. You can read more about it at the adwords blog. That tool gives you a different view of the search trends and is more like what you get from Yahoo's advertising system.
Recently I've been collecting links on interesting SEO topics. I figured I would dump a few of them out with quick reasons why I think they are good to read.
A technical read on how search engines work in general. It focuses on google but has a lot of good general information in it.
This is a recent article on how to optimize your site. I like it because it has an acronym on how to do it "camelot".
SEO chat has a lot of information in its forums.
An article from a guy who works at Google and goes into what the search engines have to deal with to keep people on the up and up. It goes into some of the stuff you don't want to be doing to try to get your site at the top of a search. For some reason I found it interesting that this guy is from kentucky.
Another good article on the "SEO Code of Conduct" AKA what you should not be doing to get your site at the top of a search.
A nice tool to help you find words to go with your website: WordTracker