With more and more teachers and schools going paperless, email/Gmail is a great tool for students to complete paperless assignments and teachers to collect, sort, and organize the work within the inbox!
For instance, have your students complete an activity where they fill out an electronic form with measurements from their worm dissection. Then have them email the results to you with a few instructions.
After some initial set up, all the teacher has to do is check their Gmail inbox to see that each student sent the message. If you include a grading rubric within the assignment, all you have to do is check the answers and send an email back with the score. Transfer the grade to your Google Doc Spreadsheet and it's off to the next assignment.
For a great screencast for setting up your Gmail for students, listen to Associate Professor Alec Couros:
Another good presentation for using Gmail, and other Google Apps, in the classroom is from Professor Alisa Cooper:
View more presentations from Alisa Cooper