I just got myself a membership at WPMU Dev where they offer premium wordpress plugins (over 100 of them) and WordPress themes.
I was interested in their ecommerce plugin (MarketPress) initially, but found that there are other great plugins that I can use more often.
Here is what I found when I joined:
GUIDES/TUTORIALS
Once I joined WPMU Dev, I learned how to set up a MultiSite WordPress installation with step-by-step instructions. This may not sound like much, but if you think installing WordPress using Fantastico was easy … this is even better. By using some plugins (listed below) I can setup a new site in seconds.
PLUGINS:
They offer a domain mapping and multiple domain plugin so that any domain pointed at the original site can automatically load the correct site on a multisite setup. No additional hosting accounts, etc. Just create a new WPMU site, map the domain and you’re ready to go.
With the blog templates plugin, I can create a template of my basic affiliate site complete with theme settings, legal disclaimers, contact forms and the actual squeeze page with headers and sales copy. Once I clone the site I simply need to edit my sales page to insert new headlines and graphics, all the boring disclaimers, css styles etc are already there.
To make the whole process run smoothly, they also offer a Multi-database option so that you can be sure of a super-fast wordpress installation that does not become cripled under heavy loads.
There are many more such as plugins to manage membership websites, theme split-testing, Advanced SEO, WordPress Directory and Classifieds scripts, etc. Be sure to go and have a look.
SUPPORT
As I mentioned before, I wanted to use the ecommerce plugin on my site. Whenever I had a problem, they were always very fast with either an answer or a workaround. I submitted a bug that I found once, and within hours there was a new version of the plugin released with the bug fixed – super!
If you use WordPress to maintain websites, and you run more than one site, go and have a look at what they have to offer. One plugin on another site could easily cost more that you would need to pay for hundreds of plugins. My membership will pay for itself many times over because of the time saved each day.
For more info, visit http://premium.wpmudev.org/