(He played Doyle on the first 9 episodes of Angel.)
First there was the LA Times obituary on Legacy.com and the Tim Minear confirmation on alt.tv.angel. Since there have been a number of articles.
Former 'Angel' Star Quinn Dies (Zap2it)
Quinn May Have Died of Overdose (Zap2it)
Angel's Quinn Is Dead (SciFi.com)
"Roseanne" and "Angel" actor Glenn Quinn dead at 32
more complete LA Times obituary
tiggz also posted a bit from an Irish poster in the BronzeBeta.
scroll down for the obit here (Yahoo! News)
"Roseanne" and "Angel" actor Glenn Quinn dead at 32 (Herald Tribune)
the long L. A. Times obituary