We use our webite as a repository of our
team history. We found it's much easier to pull it together as it's happening rather than reconstituting it years later when some of the principle players have moved on.
For privacy concerns some things, such as team rosters, are recorded but not made available until the youngest are 18.
We keep a sort of diary of the year, who we allied with, photos/videos, where seniors went after graduation, the game description and manual, the FIRST program cover for that year, the teams that went to our home regional, all the registered FRC teams for that year, our sponsors/engineers/NEMs, student college essays relating their FIRST experience, that kind of stuff. More technical content such as in-house white papers, the robot code, etc. is also kept and organized on the website.
We cut a comprehensive Team season DVD for each member each year that records special memories from pre-season, outreach, build/competition, etc. up to the year-end party (when it gets handed out).