Don't bother with keyword meta tags. They are a relic and best left
ignored. Why not spend your time writing more unique and compelling
content for your users or improving the features on your site.

:-)

Seriously, there are much more interesting and important things that
you could do in that time. For instance, you could (in no particular
order)...

- check the links on your site to make sure that you don't have any
old and broken ones,

- check your "page not found" pages to make sure that they return 404
and provide value to your users,

- check your titles and descriptions meta tags to make sure that they
are unique and relevant,

- check and update the year in your "copyright" footers,

- check and update your contact information in your domain's whois
data,

- check your statistics to find "exit pages" which might be improved,

- check your statistics and consider if catering more to international
users would make sense,

- update your sitemap file and make sure that all values are accurate,

- check out Google's Website Optimizer and think about things you
could test (perhaps a different font or color scheme?),

- or just post here in the groups about some of the things that you
have tried and how they worked out :-).

As you can see, there are a lot of things that you can do if you have
the time. These things will generally have a positive impact on your
users' experiences on your website -- and that will generally
indirectly influence the way search engines see your site as well. In
the end, if your visitors run off after coming to your site it won't
matter much that you have tweaked your keyword meta tags. Provide lots
of value for your users and make sure that your website is technically
more or less ok and things will fall into place :-)!

John