Honestly, all the API I know I have learned from various threads on here and other similar sites over the years.
If it was
this post that prompted this thread, I learned those particular API calls -- as well as many, many more that I incorporated into the XP library in my signature -- from
VBnet.
I personally consider VBnet to be a tremendous resource for good code examples of using API calls in VB6, though I find the site a bit unwieldy to navigate.
Overall, I'd say I learned the most API calls from right here, just doing searches in the CodeBank and Classic VB forums.