Cronjob plugins support automating work-flows such as email sending or creating backups. Especially for sending emails to large participant lists, automating sending email invitations reduces the risk of being treated as spam. This also applies to sending email reminders later.
Our front-end plugins improve the way questions are presented at surveys. They add additional functionality e.g. to chane the position of the other free text field or support multiple other comment fields.
For administrators we coded various plugins to make administrating Limesurvey easier. This is achieved by custom export, print or anonymizing features. Special data analysis plugins or chart dashboards can also be implemented as a Limesurvey plugin.
When it comes to security, plugins can provide alternative authorization methods or restrict access to the admin interface to certain IP addresses.