Indico is a web-based event management tool for conferences, meetings, workshops and lectures. It covers, among other things, a call for abstracts with abstract reviewing, customisable registration forms with payment integration, a drag-and-drop timetable, a badge and ticket editor, archiving of presentations and room booking. It can be extended with plugins, for instance for video conferencing. Indico is server software that you install yourself; the project site offers a sandbox for trying it out.
Indico is developed at CERN, the European Organization for Nuclear Research, a joint venture of European member states whose laboratory is near Geneva, Switzerland. CERN holds the copyright on the code, which is on GitHub under the MIT licence. No hosted offering from the developers was found on the project site, so you run Indico on your own infrastructure or with a hosting partner of your choice, and attendee data stays with you. Under the licence you may freely use modified source code, so you are not tied to a single supplier.