A Google search for "P G Wodehouse" yields over 600,000 hits. A handful are excellent, most are dross. Below is a list of my favourites.
Societies
The principal societies in the English-speaking world are The P G Wodehouse Society (UK) and its US counterpart, The Wodehouse Society. The web-sites of both offer a lot of material, including book reviews, news items about Wodehouse, and details of forthcoming events; the UK society's site also has, for those who enjoy such things (I don't!), a regular quiz.
Societies in Russia, Belgium and the Netherlands also operate websites that have varying amounts of information. The Russian site, in particular, has lots of 'goodies', for those willing to spend some time browsing its pages.
Discussion Groups
For those who wish to enjoy the virtual society of like-minded people, two email-based 
groups are worth considering (I should declare an interest, as a founder member and moderator of the first):
Blandings has over 400 members, drawn from as far afield as Australia, Canada, France, India, Ireland, Israel, Malta, the Netherlands, South Africa, the UK and the USA. As well as participating in the discussions, Blandings members have taken part in a number of collaborative projects: the annotations included here grew out of one such project, while another has unearthed and made publicly available many hard-to-find Wodehouse works that, at least in the US, are no longer under copyright protection.
The other group, WodehouseIndia, has fewer members and, as its name suggests, attracts primarily Indian fans, but non-Indians are made very welcome.
Discussion in both groups ranges from the profound to the trivial and – it must be said – those who have a decided preference for (or against) one type of discussion do not always find the environment quite to their liking. Also, some members find the volume of emails overwhelming (though a daily digest option is available for those who are unable to handle a daily inflow that rarely exceeds a couple of dozen messages).
Other Sites
Neil Midkiff's site has by far the most comprehensive on-line listing of Wodehouse's short stories. He has also written, for the Drones Club, an interesting article on 'racist' epithets in Wodehouse's work.
"Jeeves & Wooster at The Hat Sharpening Shop" is devoted to the popular "Jeeves & Wooster" TV series. Although no longer maintained, the site has a wealth of information about the series, the period, and the J&W stories in general. But be warned! The TV series took a lot of liberties with Wodehouse's stories and, particularly towards the end of the series, some of the introduced plot elements are preposterous.