We have three sorts of meetings, social, technical and hack days. The calendar on the home page of this website is the best source of information on dates, times and locations, along with the announcements email list described below.
Socials are just that, people getting together in a pub to have a drink and a chat, pub meal optional. Social meetings start about 6:30pm and happen at least once a month usually on a Thursday.
The technical meetings are held somewhere with chairs and a projector and people are invited to give talks on whatever they are working on. We have been experimenting with streaming talks via Periscope.tv and some have been uploaded to youtube. The videos are not guaranteed to be of particularly high quality but we're sort of working on it. More info on this to be added later when we're more organised - for now check the list or ask on IRC.
Hack days are held approximately every other month on Saturday afternoons at the London Hackspace. LHS has a classroom area that we book for the duration, excellent broadband and an atmosphere fairly conducive to tinkering with software and other stuff. Sometimes we have a theme, sometimes we don't. See this cheapo wiki page for a bit more information.
London Perl Mongers has two low-traffic mailing lists which are hosted by nice people at Renater on open source Perl mailing list server software called Sympa. There is a general discussion list and an announcements list. The general list is subscribed to the announcements list so you don't need to be on both.
There are also historical archives of the list, from before
June 2001 at
irc.perl.org:6667 #london.pm - you'll need an irc client, a piece of string and one of those washing up liquid bottles.