First, I'm a member of all three associations.
There is only one active MicroISV association, the ASP. Their newsgroups get 75 - 150 posts a day. They have separate technical, marketing, and general interest newsgroups. If you have virtually any question about MicroISVs you can get it answered there. It does cost $100 / year to join.
The AISIP is more-or-less dead. I posted the only new message there in the last week. (It charges a fee to join.)
The OISV is also very limited. It has a few posts per week. (It's free.)
For a crash course in Internet marketing, Adwords, Web site optimization, SEO, selling software on Amazon, and much more- come to the 20th Annual Software Industry Conference in Dallas TX next week. (July 15 - 17). It gives you a chance to meet all the major e-commerce and other MicroISV service providers and network with your peers. You can learn more there than in a year on line. For conference details see:
Software Inductry Conference