I thought I'd take a few minutes to post some tips for the Activities section of the application for those of you who are still working on your second deadline applications. (And I'm sure these tips will apply for all of your college applications, so I hope they'll be helpful.)
The most important thing is to make your list scannable and easy to read quickly. If you've ever created a resume, you've learned the importance of organizing and prioritizing the information so that the parts that you most want to communicate jump off the page. That should be your goal with your activities list as well. Keep in mind that, as with a resume, your reader isn't going to spend an hour reading your activities list--they're likely to start out by scanning, and then return to the most interesting bits to read more in-depth.
Prioritize. What is the most significant activity you've been involved in--the one you've spent the most time on or you feel has been most important to you? That is the one that should be listed first. The next most important next, and so on. Don't worry about what you think will impress the Admissions Committee most. If lacrosse is your thing, put lacrosse first. Don't list that one Saturday you spent in the soup kitchen first just because you think it looks good.
Clump activities together. A LONGER LIST IS NOT A BETTER LIST. In fact, very long lists are extremely difficult to read, and your reader will likely give up before he has reached the end. Oftentimes, students list every single community service activity as a separate entry. I would recommend listing "Community Service" as one activity and adding up all the hours that you have spent on community service for the hours section. Then use the description area below to concisely describe the different ways you've gotten involved in service. This applies to other activities as well, such as music, drama, journalism, etc.
They don't have to be "official" activities. List whatever you've spent a significant amount of time doing, not just the official, school-related activities. I read an application once where a student simply listed "Reading" because she loved reading and spent many hours a week enjoying science fiction novels. Maybe you've been teaching yourself guitar or you are constantly sketching in your journal. Let us know about those things too.
PROOFREAD. I would say 8 out of 10 applications I read have typos in the activities list. (I'm making that up, but you get my drift.) Unfortunately, because you are typing directly into your web browser, you don't have the luxury of the spell-checker. So do it the old-fashioned way: read and re-read (and re-read), use your dictionary, and get someone to read behind you to check for typos.
Hope this helps, post a comment if you have questions or if you have any other tips to share.