Do you want classic SF or modern stuff? Allamagoosa is always fun from the classics
http://web.archive.org/web/20080124051440/http://www.scifi.com/scifiction/classics/classics_archive/russell/russell1.html

for modern stuff tor.com publishes a lot of fun stuff, including short story spinoffs of novel series (Scalzi and Stross have had good stuff up there), or just look at Hugo nominated/winning stuff from any year except this year.