It's true that most search engines ignore meta keywords, the only time to
use them is to cater for mis-spellings in Yahoo. For example say I wanted
to target the phrase "frontpage behaviors" obviously I'd include that phrase
in my pages etc but a UK user would spell it as "frontpage behaviours".
Because Yahoo doesn't recognise regional spellings like this I'd want
variations on frontpage behaviours in meta keywords. It would probably also
be worth including Front Page as a keyword if I'd used FrontPage in the text
and vice versa. This would also apply to spellings like color/colour
flavor/flavour etc.
The description tag wants to be about 25 words and include a good reason for
users to click when they see your site in the search results. It's also a
very good idea to include some call to action words like buy, order,
download etc and vary them from page to page
Cheers,
Jon