Microsoft Ignite 2015 was a great event, but there were so many sessions that it was truly impossible to watch everything that looked interesting. However, all sessions were recorded and by now they should be available on Channel 9 for streaming.
Even with all the recordings available, it's hard to find the links to all sessions for a given topic. For those interested in SharePoint Server and OneDrive, I compiled here is a list of Microsoft Ignite 2015 sessions related those topics, with links to the Channel9 page with the video recording and slides.
If my calculations are correct, it would take you over 48 hours to watch all 39 sessions. So get started right now :-). Also, let me know if I missed any sessions on the SharePoint and OneDrive topics.