Also, the earlier recommendation of EscapePod shouldn't be discounted because it is audio format. Many of their stories are "reprints" and they always link the source when there's a web presence. Often, you'll find either a download or an online version at the original source. I found both Lightspeed Magazine and Clarkesworld Magazine that way.
EscapePod, along with its sister podcasts PseudoPod and PodCastle, have excellent editors. Anything they choose to present is well worth either listening to or reading.