This bit uses the Connected Lookup field from http://cl.codeplex.com/ .
What I wanted was a list containing Depts and teams within them where only the teams within a dept would show when you selected the dept when uploading content.
To do this I made a list containing the following fields:
team
dept
Then I went to my sharepoint wiki page and created a new column for dept:
Title: Department
Get info from: the list I made above
parent column: none
Value column: Department
broadcast: yes
Then another column for team
Title: Team
Get info from: the list I made above
parent column: Department
Value column: Team
broadcast: yes