I've recently been asked by a few people about the startup scene in London, and figured it'd be a good idea to write up a summary, especially for those people interested in starting a startup.
I think I've got most of the major regular events listed below, but please post in the comments if I've missed any. You can also follow me on twitter where I'll try to post info on more irregular startup events in London as and when they come up.
OpenCoffee - OpenCoffee tends towards the more practical business side of the startup scene. They meet weekly, but the real value is on the OpenCoffee mailing list which is a positive treasure trove of practical information. Most one-off startup events tend to get announced on the list as well.
London MiniBar - probably the biggest of the events, normally the format is a few talks typically some from sponsors and some from local startups followed by networking. The talks tend to be very hit-and-miss and the acoustics of the venue aren't great. However the networking is often interesting, as Minibar draws people from a wide variety of backgrounds. @MiniBarLondon
uk.news.yc - Inactive since the start of last year the Hacker News meetup used to be the best networking event in town, full of highly energized developers getting products out there. The practice of getting everyone to introduce themselves to the group was a huge plus for finding people with similar interests without having to work the room. Sadly the guys at SongKick (YC S07) who normally organized it seem to have got too busy actually building a startup to keep running it. Listing it here though in the hope it might encourage someone else to pick up the reigns and bring it back to life. Update: It's back, organized at http://www.meetup.com/HNLondon/calendar/14910886/
DrinkTank - often rated as London's best startup meetup, it has a moderated members list to try and ensure quality. They didn't accept me so they must be good.
BootLaw - Run by the well respected startup lawyers Barry Vitou and Danvers Baillieu, BootLaw events focus on the law as it applies to startups. Between them Barry and Danvers somehow seem to be at every startup event in town so if you're active in the startup scene you'll undoubtly bump into them sooner or later. @BootLaw
AppFusion - Focusing on smartphone apps AppFusion normally mixes presentations by smartphone developers showing off their new apps with networking.
The following are events I've not attended but I've seen mentioned by people active in the scene:
ebizlaw - The other regular startup law event in London, this one run by the lawyers at Fox Williams.
OpenSoho - A tech/media startup meetup.
Facebook Garage - A Facebook app developer meetup.
London Tech Startups - A general purpose tech startup meetup.
MobileMonday - Another mobile meetup.
BarCamp London - The London branch of this global unconference. Didn't run this year, but was replaced by HackCamp. @barcamplondon @hackcamp
London Startup Weekend - One of two build-a-startup-in-a-weekend events in London (the other being Launch48 below). @startuplondon
Launch48 - Launch48 is a three day event with the first day being a conference on startup topics and the next two days being startup-building. @launch48
Both Launch48 and London Startup Weekend are great events, and I'd recommend anyone thinking about starting a startup to attend them. They both follow a similar pattern of people pitching ideas for what to build, followed by a vote to get the ideas down to a manageable number. Attendees then break up and join the teams for the ideas they like most.
LSW tends to have smaller teams more focused on product building, and L48 tends to have larger teams but tends to also cover the non-product side of startups (marketing, financing, etc.) An outcome of this is that L48 generally produces more serious startups (VouChaCha, protected.cc, Wraply are all startups that came out of previous L48's and are still active).
Overall both are great events for networking and learning.
Social Innovation Camp - Another build an app in a weekend event, except SI Camp focuses on apps that contribute to the social good of society. @sicamp
Techcrunch Europe Meetups - Techcrunch Europe runs sporadic networking events in London, the mix of attendees is usually different from most startup events and often attracts more later stage startups and investors.