Reddit (/r/science, /r/askscience), Scienceblogs, viral Twitter news, and maybe here are some of the venues for myself personally. These tend to be pop-sci and general in topic.

Yep, I like more serious stuff myself. When I really want to research a subject in depth, I go straight to the academic libraries of my alma mater university across town (now often via its extensive subscriptions to databases that I can access from home with user authentication I gain through an affiliation with that university). For articles to look at for submission to Hacker News, I

1) make sure to have a science section in my Google News set-up, and additionally use Google News and Google Scholar keyword searches to check submissions by other users to HN,

2) follow the recommendations of certain key Facebook friends of mine who are either professional scientists, science writers, or science educators,

3) daily read Science-Based Medicine

http://www.sciencebasedmedicine.org/

(I don't submit to HN from Science-Based Medicine every day, but I have found some GREAT articles there over the years)

4) daily read Why Evolution Is True

http://whyevolutionistrue.wordpress.com/

(which sometimes has personal posts by the site owner but also has EXCELLENT posts by him and by guest posters on cutting-edge science issues, some of which I post directly and some of which lead to professional journal articles I post directly)

5) daily read Skeptic Blog

http://www.skepticblog.org/

(which goes from very ordinary to EXCELLENT in quality in unpredictable fashion, and has several very thoughtful co-bloggers contributing)

6) daily read Respectful Insolence

http://scienceblogs.com/insolence/

(which has had some EXCELLENT posts about the methods of research over the years)

7) receive specific suggestions of research articles to read on human intelligence and human behavioral genetics either by request or by researcher nomination from the Minnesota Twin Family Study researchers with whom I discuss issues in a journal club during the school year

8) occasionally look at Pharyngula

http://scienceblogs.com/pharyngula/

(which is going through a dry spell right now while its author finishes writing a book that I am very eager to read, but which in the past has had some great posts on topics of much interest to HN participants)

and

9) generally prowl the Web and recommendations I see anywhere else in cyberspace for good articles on science.

I test most articles I see submitted anywhere with the checklist from Peter Norvig (Google's director of research)'s article "Warning Signs in Experimental Design and Interpretation,"

http://norvig.com/experiment-design.html

which is my all-time favorite link to share in discussions on Hacker News.

By the way, a while ago there was a discussion on Hacker News about which sources NOT to submit here, and I collected some links after that discussion.

PhysOrg appears to have been banned as a site to submit from by Reddit. ScienceDaily is just a press release recycling service, nothing more. Users here on HN think there are better sites to submit from.

Comments about PhysOrg:

http://news.ycombinator.com/item?id=3077869

"Yes Physorg definitely has some of the worst articles on the internet."

http://news.ycombinator.com/item?id=3198249

"Straight from the European Space Agency, cutting out the physorg blogspam:

http://www.spacetelescope.org/news/heic1116/ (press release),

http://www.spacetelescope.org/videos/heic1116a/ (video),

http://www.spacetelescope.org/static/archives/releases/scien... (paper).

"PhysOrg: just say no."

http://news.ycombinator.com/item?id=3611888

"The physorg article summary is wrong, I think."

http://news.ycombinator.com/item?id=4108857

"Phys.org is vacuous and often flat wrong."

Comments about ScienceDaily:

http://news.ycombinator.com/item?id=3992206

"Blogspam.

"Original article (to which ScienceDaily has added precisely nothing):

http://www.washington.edu/news/articles/abundance-of-rare-dn...

"Underlying paper in Science (paywalled):

http://www.sciencemag.org/content/early/2012/05/16/science.1...

"Brief writeup from Nature discussing this paper and a couple of others on similar topics:

http://www.nature.com/news/humans-riddled-with-rare-genetic-...

http://news.ycombinator.com/item?id=4108603

"Everything I've ever seen on HN -- I don't know about Reddit -- from ScienceDaily has been a cut-and-paste copy of something else available from nearer the original source. In some cases ScienceDaily's copy is distinctly worse than the original because it lacks relevant links, enlightening pictures, etc.

" . . . . if you find something there and feel like sharing it, it's pretty much always best to take ten seconds to find the original source and submit that instead of ScienceDaily."

Comments about both PhysOrg and ScienceDaily:

http://news.ycombinator.com/item?id=3689185

"Why hasn't sciencedaily.com or physorg been banned from HN yet?"

http://news.ycombinator.com/item?id=3875529

"Original source:

http://www.nasa.gov/mission_pages/hinode/news/pole-asymmetry...

"What ScienceDaily has added to this: (1) They've removed one of the figures. (2) They've removed links to the Hinode and SOHO websites. (3) They've added lots of largely irrelevant links of their own, all of course to their own site(s).

"Please, everyone: stop linking to ScienceDaily and PhysOrg."

http://news.ycombinator.com/item?id=3867361

"Those sources don't have RSS feeds, and ScienceDaily and PhysOrg have a bad habit of not linking to such things."

http://news.ycombinator.com/item?id=4083766

"Added value in PhysOrg article: zero.

"Please, everyone, stop submitting links from PhysOrg and ScienceDaily. I have never ever ever seen anything on those sites that isn't either (1) bullshit or (2) a recycled press release with zero (or often negative) added value. (Sometimes it's both at once.) It only takes ten seconds' googling to find the original source."