First off, you picked a great time to ask this question because this week there's a free, online conference going on at https://www.dotnetconf.net/. There's a lot of good ASP.NET Core content, so you can see for yourself.

One of my favorite things about the ASP.NET team is that a lot of them were community leaders - speakers, writers, open source library authors, etc. - before being hired at Microsoft. So it's hard to pick just one or two community leaders on the team, as pretty much everyone regularly speaks at conferences, publishes open source code, blogs, etc. So it's really hard to make a short list! Hopefully this is still useful to someone.

As several others have mentioned, you really should start with Scott Hanselman (https://www.hanselman.com/ and @shanselman).
[Disclaimer: he's my boss, but I joined his team because I was a big fan long before either of us worked at Microsoft]

The ASP.NET Weekly Community Standup is a great place to connect both with the team and with the leading members of the developer community. It's at https://live.asp.net/ with Damian Edwards, Scott Hanselman and me. Damian Edwards (https://twitter.com/damianedwards) is the program manager for the ASP.NET team. During the show, I usually share 10ish links to top posts, open source projects, etc. by the community. We feel like the ASP.NET Community is made up of developers both inside and out of Microsoft, so you'll see a mix. The links are usually in the show notes, and we also tweet the links out daily at @aspnet. I'm not going to risk making a list because I don't want to leave anyone off - there are too many for me to even try to pick favorites!

Next, check out the "official" Web Dev blog: https://blogs.msdn.microsoft.com/webdev/. We have a general rule that all posts are signed by actual people, not "the ___ team", so you can see who's working directly on specific topics. You'll definitely see a lot of posts by Jeff Fritz (my team mate), who (in addition to program managing several features) does a ton of work to write up release posts, organize content for conferences, etc.

I think of David Fowler (https://twitter.com/davidfowl) as the "crazy genius" on the team. He and Damian wrote SignalR, he worked on prototyping some of the very early work that became ASP.NET Core (and .NET Core all up), etc. Check out this video to see what I mean: https://channel9.msdn.com/Events/NDC/NDC-Oslo-2017/BRK06

For front end dev, make sure you follow Mads Kristensen (https://twitter.com/mkristensen) and Steve Sanderson (https://twitter.com/StevenSanderson). Mads is a program manager for web developer tools in Visual Studio, and also writes a ton of open source Visual Studio extensions for web developers (https://github.com/madskristensen) and builds things like http://webdevchecklist.com/. Steve is always pushing the boundaries of front end development, both with things like JavaScriptServices (https://github.com/aspnet/JavaScriptServices, now shipping in the Visual Studio 2017 Angular / React project templates) and more recently with Blazor (https://github.com/SteveSanderson/Blazor - .NET code running in the browser via Web Assembly).

You'll also see Glenn Condron (https://twitter.com/condrong) listed on several of the recent Web Dev blog posts. He covers a lot of deep back end tech, including a lot of stuff with ASP.NET Core on Docker.

You can see quick (5-10 minute) interviews with most of those people, as well as a lot of other people on the .NET team, on a show that Maria Naggaga (https://twitter.com/ladynaggaga) and I started up recently called Code Conversations (https://channel9.msdn.com/Shows/Code-Conversations). These are short, code focused interviews you can watch while your code is compiling and hopefully put to work right away.

Finally, please ping me at @jongalloway if I can help connect you with anyone or if you're having trouble finding information, code samples, etc. I'm happy to help!