Sourcing
Industry Dynamics
Trimodal Distribution
It's important to understand that software engineering compensation has a trimodal distribution, as shown in the figure on the right from Pragmatic Programmer.
The highest tier are the Big Tech companies like Facebook and Google.
Salary is very roughly proportional to talent. If you are recruiting for FAANG, then it's easier to find qualified candidates at the high tier.
Sourcing Channels
LinkedIn is the dominant tool for sourcing software engineers. Below are some additional resources to consider.
General Software Engineers
University recruiting
Most universities have alumni job posting sites.
Events. Unlike business people, engineers typically don't go to events to network. Instead, engineers attend events to learn new things or build stuff.
Meetups. The Bay Area has a very high concentration of engineers. Meetups are a great way for engineers to learn about specific technologies, such as blockchain, virtual reality, and deep learning.
Hackathons. You can sponsor hackathons. When the hackathon winners win your prize, you can try to recruit them. Uber successfully did this with a couple of their hackathons. I've also had people try to recruit me after participating in a hackathon.
Online. In particular, the following sites are well-known to engineers:
HackerNews. This is a news aggregation site and forum. There are many FAANG-type engineers active on this forum because it's more technical than mainstream news.
Every month, there is a thread for hiring engineers (example: September 2021's edition). This is potentially a great source of talent because the quality of the engineers who read and participate on the site is higher than average (although not perfect). Use the search engine to find relevant profiles: https://seisvelas.github.io/hn-candidates-search/.StackOverflow. Every engineer uses StackOverflow to look up programming questions. They have a popular job board.
Github. This is a popular site for programmers to post code and improve their reputation as an engineer. See Recruiting Developers on GitHub: A Step-by-Step Guide.
Reddit. There are a couple forums with active software engineers (r/ExperiencedDevs) and entry-level software engineers (r/cscareerquestions)..
TeamBlind. This is an anonymous forum. Note, the forums on this tend to be toxic and obsessed with total compensation.
Further reading: How to Find Tech Talent on GitHub, Hacker News & Stack Overflow
Researchers
Recruiting for research is more specialized than software engineering. There are academic-focused resources you can use to source:
Conferences. Each subfield has their own conferences, some of which are hot and others are not. For Computer Vision, the most popular conference is CVPR.
Google Scholar / Arxiv. Researchers are incentivized to publish papers. Google Scholar allows you to search for papers and Arxiv is a hosting site.