It really depends on your interests. Most mainstream programming languages have dedicated subreddits, so that's a good place to start. /r/programming is a great place for general programming news, but it usually overlaps with HN. /r/netsec is another excellent subreddit with general security-related news and content.
I think the beauty of Reddit is that it's all up to you to curate the content, which obviously makes it hard to recommend things to read for others :P
Here is a list of my favorite subreddits for anyone who wants an idea of what's available on Reddit:
https://www.reddit.com/u/akkartik/m/thehumancondition
(I got the name of the second multireddit from http://hubski.com/tag/thehumancondition. Hubski is another interesting community.)