Based on our record, Google Design Sprint Kit seems to be more popular. It has been mentiond 1 time since March 2021. We are tracking product recommendations and mentions on various public social media platforms and blogs. They can help you identify which product is more popular and what people think of it.
Also Google (as in the company not the verb) has a free version of their discovery techniques here https://designsprintkit.withgoogle.com/. Source: about 1 year ago
Design Sprint Kits - A pre-assembled kit for GV design sprints.
Warmup Inbox - Warmup Inbox is a tool that automates the process of warming up your email inboxes, raising your sender reputation and inbox health automatically.
Design Principles - An open source repository of design principles and methods
Warmbox.ai - Warm up your cold email inbox, and never land in spam anymore!
Sprint - How to solve big problems and test new ideas in 5 days
MailReach.co - The #1 email warming service to improve your deliverability by generating realistic and meaningful engagement to your emails. Easy-to-use solution to help you land in the main inbox instead of the spam folder.