I like the recommendation of the ‘about us’ page being developed as a kind of ‘home page’ to the area of a company’s site that detailing operations and business movements. This seems to me to be a great candidate for sub-domaining, to me.
Custom 404 pages, I think, might be weighted fairly heavy in the not-too-distant future, if the toolkit released by MSN in June 2008 or Google’s 404 widget release in late Aug 2008 are any kind of indication. When MSN and Google move toward the same goal, one should take proper note! Not only does a custom/dynamic 404 page clearly enhance overall user experience, but when a crawler gets to ‘something crazy’ when it was spidering ‘something relevant,’ you now have the ability, on a custom 404 page, to redirect the bot back to a 200 URL with relevant info. Happy bots = happy SEs.
Robots.txt: Have one, even if it’s blank!
Sitemap: Be sure to have 2 versions: One for bots, and one for humans.
Good, general tips, but I think there’s reason to institute custom 404 pages.