I am going to using Trello to collaborate with school personnel on a study. I need to upload video and audio recording files that will be larger than the 10 MB limit. Anyway to accommodate us? Can we purchase extra space?
It is not currently possible to purchase more space right now.
However, they just released (August 22, 2012) Google Drive integration, see their blog post Introducing Google Drive Integration on the Trello blog. It allows you to attach files from your Google Drive account. The upload limit is limited only by Google Drive's limit, which is 10GB according to Google Docs size limits.