While Apple stopped selling them on-line at some point in the Spring, AT&T has been selling their existing stock at their stores. Also, AT&T has had refurbed iPhones available at their refurb area, as late as May 31st.
Long story short, if you want a 1stGen iPhone, check your local AT&T stores. I wouldn't expect any sale prices, either. But, hey, you never know...(bunch of threads on this topic though)
Seems like Apple did a pretty great job (no pun) of timing when to stop producing 1stGen iPhones to create that "shortage" feeling...