I found this plugin to be just what I was looking for.
I could find no other plugin that deals with "OR/AND" for displaying categories. I can see that this plugin doesn't have much in the way of documentation, which could explain the lackluster response. It's a winner in my book!
This effectively allows me to minimize the amount of categories I need to create, and then just pull posts that only rest in BOTH categories.
For example, rather than having to create a total of 25 (current) categories:
• Winter <-2
• Spring <-3
• Summer <-4
• Fall <-5, etc.
(on back to 2007... and in the future)
I can have just 9 (current) categories and simply filter the posts by requesting 2011/winter, 2010/winter, etc:
This plugin effectively allowed me to eliminate having to create redundant/nested categories, and only 1 category will need to be added per year. Wahoo! Thank you, Mapelo! I owe you a beer or a coffee! How can we make that happen?