meta keyword tags are still useful to a small degree with the bigger search engines. They still read it and you can use it to target some common mis-spellings of your keywords, that way you don't have to work out how to get them into your copy without it looking ridiculous. Also many smaller and niche engines still use them and some directories will not list the site without them. So use them, put it on every page and make each one relevant to the page rather than use the same ones globally.
The meta description tag is a different situation this is important because all engines do read it. The text contents of the tag can and will be used on the results page for a search and in some engines is the only thing shown. Google especially, will do this if the search term is not found in the visible page copy or is an off site factor (IBL anchor text or an image alt attribute in a linked image for instance). And as such should be on each page and relevant to that page.
What they aren't anymore is a "magic bullet" to good positioning.
Chris.
Indifference will be the downfall of mankind, but who cares?