Just wondered about what you all do?
I am constantly updating our website in my job on a daily basis.

* Updating new products
* Removing obselete products
* Updating pages for SEO

I have the Sitemap.xml file configured for Google through the Webmaster Tools, the URLLIST.TXT file for Yahoo, and continually
monitor my webmaster tools account for error 404 pages, etc.
How often do you upload the sitemap? At the moment I can
update/upload this sitemap 3-5 times per day.
Should I just be limiting this to once a day? Or even once ever other day?

Since we are constantly adding new pages to our site, we typically update our sitemaps once per day. We actually built a way to automate this. It's fine if you want to update your sitemaps more than once per day but it's probably not necessary. If you are constantly making changes to your website, you might just want to wait until the end of the day or the next morning to update your sitemap. Just for sanity's sake. :)

it will really good if you generate your sitemap when make a new post. For wp user, there is a plugin I use to generate it automatically. if not wrong, it's called xml sitemap generator

it will really good if you generate your sitemap when make a new post. For wp user, there is a plugin I use to generate it automatically. if not wrong, it's called xml sitemap generator

It is nice to see WordPress is having plugin. What about Zen Cart. Which software (freeware) would be the best one to generate SiteMap.xml file for Zen Cart.

Many of my clients use CMS software for their websites and my understanding is that the sitemaps automatically update whenever new content is added. Is this true or should I be checking with my clients to make sure that they update the sitemaps manually on a regular basis?

I use an add-on called simple xml sitemap on my zen-cart sites and it generate sitemap for my sites daily and ping the top 4 search engines. :)

apache mod_rewrite in .htaccess

RewriteEngine ON
RewriteRule ^sitemap.xml? makesitemap.php

sitemap generated from the database whenever anything looks for a sitemap