Skunkworks uses
http://groupspaces.com/ to manage email lists. There is a cost, but we like the tool better than Google Groups. Each sub team has its own list. Other tips include: keep it short, make fun, & copy the parents.
To maximize impact, send fewer well organized emails. Groupspaces creates a table of contents of the topics covered to allow team members to scan for those that they are interested in. Use clear titles, and bullet the who, what, where, when at the top of a topic. You can include narrative but understand you will loose most of your audience for that part.
We include a list of links to fun articles about robots and technology at the bottom of emails. We also from time to time include instructions in an email on how to be included in a drawing for a $20 Starbucks card. At the start of the meeting award the winner and thank all the people who entered.
Copy parents on most emails. All parents are on the "student" list. We also have a "parents only" list for rare communications that require it. Student's hear most important items in the meeting and parents see it in the email.