UPDATE: Reddit content, particularly in certain sub-categories, is very high quality. Far superior to all Digg versions.
Site does have some adult content, but those sections are clearly denoted as NSFW. Reddit user interface offers option of blocking visibility of NSFW (or any other sections perceived as objectionable).
Social bookmarking site with active online community. User interface is a bit daunting at first. I liked the old Digg, version 3.0, better, but that is no more. Certain categories include educational discussions and helpful reference links.
Reddit itself is one of the safest sites on the web. This site goes under both the Useful and Informative category and the Entertaining one.
This site is almost 100% community based and upheld. Uses community made separate forums[subreddit's] that allow's anyone to submit a link or text based submission upon that subreddit's rules and reddit's own short set of rules. Like I said, it's safe but the community aspect may make it not safe for work.
Have to agree with many below, Reddit is definitely better than Digg in that it's much more informative and interactive and there's less shameless marketing going on.
However the Reddit community is sometimes overly critical and takes itself a bit too seriously at times.
Overall, great site, lots of fun and full of awesome articles and information.