http://www.sluggy.com - Probably the best web-comic on the net, Sluggy Freelance expertly blends all known genres together and masters them all. The first online comic I ever read and one that inspired me to create Rooms. Excellent stuff.
http://www.joyceandwalky.com and http://www.shortpacked.com - David Willis is a master artist and storyteller who has managed to create a coherent universe through three distinctive web-comics. Start with the original Roomies, read through It's Walky! And experience the joys of all-new Shortpacked and Joyce & Walky!
http://www.pvponline.com - Player Vs. Player is a comic about the staff of a gaming magazine and the wacky adventures they get into. Despite this, it actually has very little to do with gaming anymore. No matter - the characters, plot and humour are all top notch.
http://www.digitalpimponline.com - Joe Dunn just never stops making comics. This is evidenced by the fact that he has three regularly updating comics: Joe Loves Crappy Movies, Marticulated Wednesdays and Turtle Vs. Bunny, all of which are awesome. Check 'em out!
http://www.theaterhopper.com - Theater Hopper is a light hearted look at movies and the film industry where the lead characters are, rather surprisingly, a married couple. Good fun for any supporters of the silver screen.
http://www.multiplexcomic.com - Another movie based comic, this time set around the staff of the multiplex cinema. Good humour and the artwork is refreshingly different.
http://robandelliot.cycomics.com - The 'soon to be ex' artist for Saturday Sluggy strips and his brother present a web-comic about two guys and the crazy circumstances they get into. Wacky, well conceived fun.
http://www.gunnerkrigg.com - A comic about young girls at a boarding school. Sound dull? Think again. Ghosts, robots, demons and crazy wolf things with wooden arms – all in a day’s work at Gunnerkrig Court. Great art and humour.
http://www.afterstrife.com – Got linked to this at the old UK Webcomix thingamajig. It’s a fantasy comic about life after death with an intriguing concept behind it. I wasn’t sure which way it’d go when it started but it’s starting to hot up now. Well worth a read.
http://www.xkcd.com/ - Surreal, clever and a little bit nutty. Xkcd tickles my funny bone so check it out.
Comics by People I know
http://www.jump-leads.com/ – Ben Paddon's brand new webcomic, it's a collaborative effort between him and an artistic chap by the name of JjAR. As someone who is going to be writing for this, some time soon, I can tell you now that you're in for one hell of a ride. Finally, a sci-fi comedy comic that actually works!
http://www.fried-comic.com/fried/ - Created and drawn by Ben Paddon, Fried was a comic about a guy called Joe, his friend Reg and a talking hamburger who thinks he's better than both of them. I co-wrote this, from 2004 onwards and was sad to see Ben terminate it. Fried was also set within the Psycheverse, so is well worth a look for Rooms fans.
http://comic.apathysketchpad.com - It's hard to exactly pin down what Apathy is about. But it's funny, and set within the Psycheverse. So go read it. NOTE: Sadly, this too has fallen by the wayside and seems unlikely to return. Still, the archives are well worth reading.
http://bootcamp.comicgen.com - Bootcamp was a comic about worms in a military training camp. It's very droll British humour and thoroughly entertaining. Sadly, it hasn't updated in ages. I guess people I know just aren't very reliable when it comes to webcomics.
http://www.lunchbreaktoons.com/bfc/arch.html - Jamie McGarry's Built for Comfort comic continues the trend of comics by people that I know, which have subsequently ended. However, there's always the archives for those of us that want to relive the Yorkshire-based hijinks.
Other stuff you might enjoy
http://www.scifi.com/scifiwire/ - Whether you love or hate the Sci-Fi Channel, they do provide a good daily news service on all Sci-Fi related Film and TV news.
http://www.bbc.co.uk/doctorwho/ - The official Doctor Who website.
http://www.roosterteeth.com - The Rooster Teeth website is home to a great range of content, such as the machinima series', 'The Strangerhood' and 'Red vs. Blue' along with a rather amusing comic strip about the guys who make them.
http://www.telltalegames.com - Home to the new Sam & Max episodic game series. Check it out, today!
http://movies.lionhead.com/studio/Movie-Mad - My movies made in The Movies, including a Rooms prequel.
http://www.smashbros.com/ - It's Smashing!