The HP48 has one popular Usenet newsgroup: comp.sys.hp48. For those who haven't seen it before, comp.sys.hp48 is the best place on the Internet for discussion about HP calculators. News about new programs is also available, as well as technical information about the calculator. If you have a tough programming question not answered in the owner's manual or the FAQ, chances are you'll get an answer here. Comp.sys.hp48 is a very friendly "community," and unlike many newsgroups, it gets almost no spam.
There are also several others, but they aren't very commonly used. Comp.sys.hp48 gets about 1500 posts each month and is unmoderated. Comp.sources.hp48 was a moderated group for binaries, but it is pretty much dead now without a moderator. Comp.sys.hp48.d was originally supposed to be an unmoderated discussion group (comp.sys.hp48 was originally moderated), but in mid-1990 it was obsoleted by the new comp.sys.hp48. Fido.ger.hp48sx is a German newsgroup, and es.comp.sistemas.hp48 is Spanish (you may read it online at this address). Hp48.programming on news.hpcalc.net (not affiliated with hpcalc.org) is a commonly used French newsgroup.
There are a number of people who consistently contribute useful articles to comp.sys.hp48. I could list dozens, but to keep things short, only a few are listed below:
To read comp.sys.hp48, try this link: comp.sys.hp48. If that doesn't work, ask your ISP for information on configuring your newsreader. If your ISP doesn't serve comp.sys.hp48, you can read it on the web at Google.