Yes, you can make a difference!:
Make it clear to your representatives that you support the actions of Ed Snowden and ask that he be treated as a whistleblower and patriot. A phone call or written letter is effective. Sending a letter and then following up with a phone call is best.
Make it clear to your representatives that you are against the NSA program and all others like it that we don't know about (and explain exactly why). Having talked to people who have worked on the staff of Congresspeople I know that a phone call makes a good amount of impact, an email you wrote helps but is less effective, but if you know you are too lazy for that click here and do this. I've been informed by /u/secondlogin that "as few as SEVEN personally written letters to a representative can turn their attention to a given subject. NOT EMAIL SPAM. A personal, written letter will be put on the top of their mail stack and taken directly to the Rep."
Find out who your representatives are and post a tasteful, well-written message on their Facebook profiles. This is somewhat effective because it is "public." It raises awareness of the issue and if there are enough concerned people commenting they (or someone from their staff) will often respond so you can have an actual dialogue. I did this during the CISPA uproar and actually had a conversation of sorts on the issue with my Congressman. Tell your representatives you support this bill.
Contact the "Intelligence Gang of 8" and let them know their actions are a reprehensible betrayal of the American people's right to privacy: Representative Mike Rogers, Representative Dutch Ruppersberger, Senator Diane Feinstein, Senator Saxby Chambliss, Representative John Boehner, Representative Nancy Pelosi, Senator Harry Reid, and Senator Mitch McConnell
Call and/or fax the office of POTUS: President Barack Obama Phone:(202) 456-1111 Fax:(202) 456-2461
Follow up. Call back and ask what progress has been made or what new information they have available to you regarding your last call. These people represent you — it is okay to hold them personally accountable to you (but don't overdo it or you'll be dismissed as psycho and your opinion will matter less).
Watch how the government handles Ed Snowden. If he is mistreated we should organize and protest.
We should organize and protest against the NSA spying program (among other issues). I am a supporter of /r/Occupy because I believe it is the movement with the most steam and potential. It isn't perfect but I'd rather not sit around and wait for something better to come along.
"Sign" the petition to repeal the Patriot Act . "Sign" the Avaaz petition about PRISM. "Sign" the whitehouse.gov petition to pardon Edward Snowden. While this is better than doing nothing, it's not doing much so don't give yourself too much credit. Contacting your reps is much more effective.
Snowden plugged /r/restorethefourth and if we support him, we should participate in that in his honor. Don't consider this having actually done anything to help but subscribe to /r/restorethefourth to stay aware in the future.
Talk to other people about the issue as you go about your day. Inform people of what happened and make sure you explain why it is wrong and how it can be misused. Encourage them to take the actions above.
Feel free to copy and paste this post whenever you encounter someone on Reddit who says, "But what can I do about it?"
BONUS: Fight these thoughts (that lead to powerlessness and inaction):
"I can't make a difference because I am one person."
"Someone else will fix it."
"It's too late."
"I'll worry about that when it effects me personally."
"There is nothing I can do about it."
"I am a lazy, selfish human being."