The catalyst: By day, blogger Laura Miller, 32, worked as an administrative assistant at Duquesne University in Pittsburgh, Pennsylvania. Her busy workload -- booking schedules, managing projects, and fielding inquiries from students and the public -- didn't allow much time for another important thing she neglected on her to-do list: good will.

The Secret Agent L idea blossomed in July 2009, after she asked one of her blog readers, whom she had befriended, what she wanted for her birthday. Her friend replied, "Don't send me anything; just do a random act of kindness for someone else." They talked about the "secret mission" and even came up with the moniker and tag line: "Secret Agent L, All Around Swell Chick." The self-proclaimed spy girl was up for the challenge. "It was exciting. I thought, fine, I'm going to do something fun." She plotted. Caught up in the excitement, Miller even made Secret Agent L business cards with her blog URL.

Busy with work, she asked her co-conspirator, Vivian Lee Croft, a friend and co-worker, to help her with mission No. 1. Miller attached a homemade business card with thick green ribbon to her first gift, a stem of lavender hydrangea, and asked Croft to leave it on a stranger's windshield wiper.

The first blog title: "Unleash the kindness." She wrote: "It begins. Today we start to unleash anonymous acts of kindness and day-brightening all over Pittsburgh."

"I thought the flower, picked at a nearby garden, would brighten up anybody's day. Who could be upset when looking at a flower?" Miller explained.

The act: Her gifts, about $5  to $10 each, fit her admin salary: coffee gift cards, a roll of quarters wrapped in pink and green ribbons at a Laundromat, sunflower bouquets at graves of fallen soldiers on Memorial Day, colorful cards filled with inspirational quotes in public parks and bathrooms.

The first three weeks she carried out and blogged about her mission every day, signing her entries Secret Agent L. She slipped into a bookstore bathroom and left the note, "Happiness is the experience of living every minute, with love, grace, and gratitude."

Quickly, words of appreciation filled her inbox. Nearly a month into the project, though, she realized that giving every day would bust her budget.  She called for backup and encouraged readers to execute their own secret missions across America.

The ripple: She received a few responses at first, then dozens. Soon, Miller recruited more than 80 worldwide secret agents in Canada, Denmark, Germany, England, Japan, and Mongolia. The clandestine acts were both creative and practical. One agent gathered a note, a coupon, and enough cash to buy a bag of diapers, then left the items at an diaper-changing station in a public bathroom.

Miller blogged about her drop-offs and Affiliate Agents' good deeds. She also suggested follow-up acts: "Mission: Holy Coffee! What better place to leave a kind gesture than a church? Maybe the person who stops in for morning Mass tomorrow will treat a friend to a cup of joe afterwards. Wouldn't that be a great start to the day?"

A local Pittsburgh TV news station featured the secret project. Then other TV networks, bloggers, and websites helped her message go viral at Kirtsy.com, the Huffington Post, Reader's Digest, CNN, and Fox News.

These days, Miller receives about 1,000 daily blog hits, and she's received more than 2,500 email testimonies about these simple, thoughtful, inexpensive gestures. Nathan in Pittsburgh emailed,  "I sat down on the park bench next to the package and read the words on the front of the envelope over and again: "For you! Yes ... you!" But, surely, it couldn't have been for me. Why would it be? But then, what if it was...? I was touched by this random act of kindness. Call it serendipity, but just when I was losing hope in myself and life's purpose, something like this comes along. I'll be sure to keep myself open to other little gestures that may be out there, keep trying, and, of course, pay it forward when I can."

George from Massachusetts wrote about finding a card in a restroom on top of Mount Everett, the fifth highest peak in Massachusetts. "When I first opened the card, I was overwhelmed -- I sat there and cried, wondering how did you know, how wonderful it was that you thought to leave that card for me. Thank you from the bottom of my heart."

Exactly one year after Secret Agent L launched her project, she revealed her identity. "I saw the positive response the project was getting. I wanted to get out in the community as a real person to see what I could do to spread kindness," said Miller. So far, she and her Associate Agents have completed more than 300 missions. "How easy it is to pay attention to the people around you," Miller says. "Imagine what 2 to 3 minutes could do to brighten someone else's day. It's the easiest and simplest thing to do."

--Toan Lam