What is the URL we should use to activate the Crucible and Jenkins plugins with Jira OnDemand?
We have an internal instance for each that we would like to configure and get integrated.
Jenkins allows you to directly update JIRA (i guess it is SOAP interface) when an issue is picked up for build in the post functions section of the job configuration. It also allows to automatically release versions in JIRA.
These does not require any plugin inside JIRA as Jenkins directly uses the existing SOAP interface and I assume it should work for OnDemand too.
I have no clue about which Crucible Jenkins integration you are talking about.
I'm not sure how to help you with Jenkins, as it's not an Atlassian product.
It's unfortunately impossible to associate Standalone instances to OnDemand instances, due to many firewall restrictions, among other things.
Basically, you need to have JIRA OnDemand + Crucible OnDemand, or JIRA Standalone + Crucible Standalone.
This means that you won't be able to add Crucible Standalone plugins to your JIRA OnDemand instance.