Botletter is a similar service as Mailchimp, but instead of using emails we use Facebook Messenger.

Hunter is the leading solution to find and verify professional email addresses. Start using Hunter and connect with the people that matter for your business.

StartupStash is a curated directory of tools and resources to build your startup. All the startup resources you need to build a killer product.

Slik helps create more effective cold outbound campaigns by deanonymizing site visitors.

Standuply is the #1 Standup Bot. It runs asynchronous stand-up & retrospective meetings, Slack polls, and tracks team performance to automate your Agile processes.

Project management Tool Casual.pm has developed a unique interactive "how to" guides for startups called "Startup Toolkit". The guides are FREE to use.

www.MyTweetAlerts.com is like Google Alerts but for Twitter. You can receive alerts and get emails when someone tweets about some topics and the tweet has more than X likes or Y retweets. You can also get emails if someone tweets about some keywords and he/she has more than X followers. So it is really useful to find tweets that can go viral.