If I'm running a small minyan that sometimes has a quorum and sometimes doesn't, and I'd like to only hold the minyan when I know we'll have ten, is there an online tool to help me manage this?
http://www.minyanman.co.za/ is a Minyan management tool.
Minyan Manager is a community service to help people manage business minyanim. We know how useful it is having a mincha minyan at work but how time consuming it is to manage it, as well as how frustrating when people come and yet a minyan is not present. We hope this will reduce the administration and encourage more companies to have a mincha minyan. For more information contact firstname.lastname@example.org
JPal should solve this issue.
Please check this thread on SE: Davening with a Minyan in China
Minyan On Demand let's you create a minyan anywhere in the world and instantly have thousands of users notified. Ideal for international business travels and anyone looking to pray with a minyan where there's no permanent minyan available.
You might try Google Calendar; this way you can invite folks, and their responses will be shown in the meeting entry for each tefillah. Of course, this assumes that people live up to their responses!
You can always create a Facebook page for your Minyan and send out Minyan times on a daily basis to people who voluntarily subscribe, and then ask participants to reply by a certain time if they plan to attend.
https://synago.io does this:
This is Synago. Automagic minyan planning and scheduling of synagogue services in the diaspora.
http://www.doodle.com/ is a good resource for organizing peoples' schedules