I needed Wildcard DNS for WordPress 3.0, for the new Multi-Site features. I have WP3.0 Multi-Site (Subdomains) working on a shared hosting account (the $4.95/month kind). It might work on a lot of hosts, I’m using LunarPages.
I set up wildcard DNS from CPanel, simply putting * (asterisk) in the subdomain name, for each domain I want blogs for (mydomain.com, myotherdomain.com, mythirddomain.info, etc).
The only thing I needed my hosting provider’s help with was moving my existing site from public_html to an add-on domain (they had to change the server’s DNS record); I didn’t want my web site and WordPress in the same folder. No need to have them figure out the correct A records or CNAME records, so if it works in your hosting account, this is much easier.
I had to install WP3 in public_html for it to work, even with the wildcard DNS working; the Multi-Site features wouldn’t work with WP installed in an add-on domain. (Said another way, WP3 had to be in public_html.)
In this setup, creating a sub-subdomain, e.g. chess.blogs.mydomain.com, makes a folder chess in public_html, not in public_html/blogs. So you’d have to include that in your mapping. I haven’t tried using the Domain Mapping plugin to map to a sub-subdomain such as anything.blogs.mydomain.com; it does work fine for anything.mydomain.com.
I made a blog post with instructions for all the changes I had to make, to have my existing web sites work and to have WP3.0 work multi-site, at WordPress 3.0 Multi-Site Installation with Existing Web Sites.
