Now that I've reached $1,000 MRR, my next big goal is to get 100 paying users in the next 100 days. Source: almost 2 years ago

If you're interested in joining the challenge the signup form and leaderboard are at https://100in100.co/. Source: almost 2 years ago

This month we're hosting a free group challenge for SaaS founders. The goal is simple: get 100 new paying users in 100 days. Source: almost 2 years ago

This last year we went from about 400 members to now over 2,000 (counting by active Slack members). A lot of the growth came from a challenge we ran called 100 users 100 days. The idea of the challenge was to get 100 new paying users in 100 days, with a leaderboard and weekly mastermind sessions for accountability. Definitely hope to run another round of the challenge soon. Source: over 2 years ago

- Try a public challenge like http://100in100.co. You'll get grouped with other entrepreneurs who are learning just like you. - Source: Hacker News / about 3 years ago

I've used woobox among others to run sweepstakes on social and you can absolutely track comments, shares, likes, follows etc. Source: over 1 year ago