Right at this moment, hundreds of secrets are traveling through the mail or through the ether to feed secret-sharing communities PostSecret and Whisper.

PostSecret, the older of the two, helps people find release through postcards. They decorate a card with a secret and mail it in, and PostSecret chooses around 20 secrets to share every Sunday – secrets that the sender has never told anyone before.

Since PostSecret started in 2004, founder Frank Warren has collected over half a million secrets. Its forums have millions of posts where people commiserate, discuss, and connect around their revelations. PostSecret has spawned art exhibitions and four books: PostSecret: Extraordinary Confessions from Ordinary Lives; My Secret: A PostSecret Book; The Secret Lives of Men and Women: A PostSecret Book; and A Lifetime of Secrets: A PostSecret Book.

“Secrets can take many forms – they can be shocking, or silly, or soulful. They can connect us to our deepest humanity, or with people we’ll never meet,” says Warren in a TED talk. “Secrets can remind us of the countless human dramas – of frailty and heroism playing out silently in the lives of people all around us.”

Warren now travels around the world giving presentations on secrets, then inviting the audience to share their secrets in person.

If PostSecret takes things slow and deliberate – each card is crafted by its sender, then the best ones make it to the site – then Whisper is secret-telling for the digital generation. You can snap a photo, add a secret, then post it instantly. The iPhone app already has over 1 million users, and just raised $3 million in funding last week.

“Whisper is about expressing your true self within a community of honesty & acceptance.”

Whisper builds in even more social features, letting you comment on photos and chat with other members (anonymously). PostSecret’s app was shut down a few months after it launched in 2011 due to spam and inappropriate postings; we’ll see how Whisper fares.

These two products are alike in their wild popularity. One theory is that they combat the rosy pictures we paint on non-anonymous social networks like Facebook. We get a peek into the true lives of others – which, perhaps like our own, are a little messed up.

For the people who post, it’s also an outlet. Even when we’re not honest, secrets clamor to be let out – somewhere. Warren says that the process of sharing secrets can be healing. Could sharing secrets with friends and family, rather than strangers, be even more healing?