From the referer (sic) data in my web server logs (which is not completely reliable but still offers some insight), the three largest sources of traffic to my website are:
1. RSS feeds - People using RSS aggregator services as well as local RSS reader tools.
2. Newsletters - I was surprised to discover just how many tech newsletters there are on the Web and how active their user bases are. Once in a while, a newsletter picks up one of my silly or quirky posts, which then brings a large number of visits from its followers.
3. Search engines - Traffic from Google, DuckDuckGo, Bing and similar search engines. This is usually for specific tools, games and HOWTO posts available on my website that some visitors tend to return to repeatedly.