There are many excellent sources nowadays. Especially if you're into physics or economics but not necessarily.

The most general is the Daily Roundup at National Affairs where you get titles and abstracts of papers fitting the daily theme (lousily). RSS available.

http://www.nationalaffairs.com/blog/blogger/findings-a-daily...

For arXiv there are blogs highlighting papers, like this one

http://www.technologyreview.com/contributor/emerging-technol...

For economics, be sure to subscribe to the RSS feeds of NBER and IZA. Note that those are not reviewed.

http://www.nber.org/rss/

http://www.iza.org/en/webcontent/publications/papers

Availability varies. But you can usually find a prepub by just Googling.