I wish I had more examples, but all I can really think of is the fact that sites still offer RSS feeds for reading articles.
Thinking back to the good old days, my main forms of discovery were IRC, Usenet (with its underlying structure it made it easy to dig into weird/different niches at will)...
A few things were consistent about these mechanisms: Each one allowed you to start in a specific niche/community, explore outside of it and become entrenched in wider/more diverse communities/interests.
They had some basic structure (channels on IRC, top level groups on Usenet), some form of curation/moderation (channel operators, news server admins who could white/blacklist content, rules/guidelines about cross-posting, some proactive moves against spam/off topic trolling), but ultimately were "open."
Anyone could get their foot in with some basic software, anyone could add their voice, and engage either with a group of people or one-on-one.
These days, about 70% of my exploration online starts at HN. There's a bit from Kottke and Coudal, a couple of Twitter feeds, and various music labels (Stone's Throw, Mad Decent).
Is Delicious the answer? It's got tags for bookmarks _and_ discovery -- there go two of the HN front page stories from this past week. Remap Ctrl-D in Chrome, and I don't think you'll find a better, more open solution for the Web out there.