Yeah Slashdot started it for me too (well IRC, but website-wise the first was Slashdot). I'm a high school drop-out (now 31) who somehow managed to make a comfortable career off web development and IT project management thanks almost entirely to "sponge learning" off IRC, Slashdot, HN (more recently) and the Internet in general.
I've never done any formal training, I just wholeheartedly believe in immersing yourself in what you want to learn, and specifically immerse yourself at a deeper level than you're comfortable with to force yourself to work harder.
I can quite literally say my entire adult education from Year 10 onwards came from the Internet, and I owe my career, house, vehicles, all of it to sites like HN :)