Apart from Admidio which has already been mentioned, another option to explore is CiviCRM. Source: about 1 year ago

As a software developer, I looked at some of what they did, and some of what is commercially available for candidates. The guy who won in the races I ran in was spending $1500/month for a website that was a simple brochure. Something that could be set up for even folks running for school board might be a simple hosted brochure/blog site with Wordpress as a front-end, with CivCRM keeping track of volunteers and... Source: about 1 year ago

Https://civicrm.org/ [this works with a cms like drupal, wordpress, joomla etc]. Source: about 2 years ago

So far I found Chatwoot, CiviCRM, Corteza, ERPNext, EspoCRM, Dolibarr, Odoo, OroCRM, Mautic, SuiteCRM and X2CRM and there are probably even much more available. It seems that Odoo and ERPNext are huge but also very flexible (with many extensions available). Source: about 2 years ago

If you are already using wordpress, you may also want to look at CiviCRM [https://civicrm.org/] for managing members etc. It is used by non-profit orgs. Source: over 2 years ago

Is there a plugin that'd support something like signup.com or doodle.com ? Source: about 1 year ago

I use signup.com, and it has been pretty good. You can set when the reminder email goes out, so I changed it to 24 hours. They get a confirmation when they sign up, a reminder 24 hours before, and a link to cancel. My only issue is when students log in 5 minutes after the meeting is scheduled and then I get an alert that they have rescheduled, but most don't do that because we are a fairly small school and they... Source: over 2 years ago

I've used signup.com and signupgenius.com in the past and both worked well and have free options. But in looking around, volunteersignup.org would be my pick now and seems to be exactly what you're looking for. Source: almost 3 years ago