The new edition of D&D has inspired a large number of people to "roll their own," and with modern desktop publishing tools being available so cheaply (or even free), it should come as no surprise that a lot of it is really polished. Here are a few sites that I find particularly useful; I can't swear to the balance of all of their materials, but there are some great ideas in there and some very polished game elements I use myself.
Both of the below blogs I found through Reddit's /r/UnearthedArcana subreddit. Anyone can post there, and some of the stuff is very unbalanced, but it's a good clearinghouse for material.
BoltNine Homebrew is the blog for Reddit user /u/AshenGT, but he/she's posted material put together by other people as well. AshenGT seems to be working up the League of Legends Runeterra setting for D&D. I've used critters from this blog before, and some of the subclass options look interesting.
Walrock Homebrew is the blog of Reddit user /u/the_singular_anyone. He/she seems to concentrate on subclasses, and most of the material is currently for Paladins and Warlocks. I like the Invocation Drawbacks idea.
5e Grognard is not a blog I got to through Reddit. Jon was a poster to the defunct Wizards of the Coast Community boards, where he had a series of posts where he converted old material from old issues of Dragon magazine to new rules. I found a lot of his conversions solid, and appreciated that I wouldn't have to do my own. He's on ENWorld (as Bupp), but I haven't seen much lately. Regardless, I support his Patreon.
Speaking of ENWorld, the site has a D&D House Rules, Homebrews, & Conversion Library subforum. Morrus (the administrator) also has started a Patreon called En5ider, which produces articles for D&D 5E, including new class and race options; En5ider is a subscription-based service, but it's inexpensive compared to a magazine subscription.
EDIT: And another good homebrew blog is the Sterling Vermin Adventuring Co., hosted by /u/coolgamertagbro.