Some claim it has grown out of the goth culture (losing all the emo bits presumably) or the sci-fi genre. I don't know about that but I know it describes the things that make my heart go pitter-pat when I see very lust worthy items - like old books (swoon), libraries full of old books (double swoon), anything to do with clocks, clock parts, old watches, velvet, inlayed wood, steamer trunks, anything to do with old fashioned travel (think trains like The Orient Express) or ocean liners (like Titanic - but hey - no icebergs thanks). Literary influences on steampunk include anything Jules Verne naturally and other writers of that period who wrote about the future.
One of the best blogs is The Steampunk Home - I spent most of the day avoiding the heat and the whining of children by immersing myself in the blog from start to finish. Can't say that I totally agree with all the calls re: steampunk or not - but hey - that's the whole thing - it has that certain je ne sais quoi - and probably can encompass people's particular pecadilloes (as opposed to armadillos - although a stuffed one would possibly qualify - as taxidermy in the Victorian pseudo scientific taste can be encompassed by the look although I am personally not big on the dead animal thing!)
When I finished reading and drooling at all the pics - I thought of all the steampunk style things I have loved over the years - what actually occurred to me is that some of my all time favourite computer games are very steampunk - Myst (and its follow up games such as Riven and Exile) are very much in the genre, as well as the various Zork games (written by Activision) particulary Zork Nemesis. Now the truly scary thing is that these games are at least 12 years old in the case of Zork Nemesis and 10 or 11 years old in the case of the various Myst games. Wow - am I ahead of the times or what???
Other things I love that I think have some steampunk influences in them are of course movies - The Golden Compass is one of course - the storyline didn't do much for me but I loved all the costumes and set designs and of course - the gadgetry - not the least of which was the aforementioned compass and the airships and Daniel Craig who isn't the least bit steampunk but maybe a steamy hunk which is close enough in my book.
And then of course there was The Spiderwick Chronicles - which I might also add got a mention on The Steampunk Home because Holly Black the co-creator of the aforementioned book has a Secret Library which is accessed through a hidden door. Sheesh! It's enough to almost motivate me to go and write a best selling book for kids so that I can afford to have one too. (Can you tell I am only slightly jealous? I wonder if she'd let me come and sit in her library and inhale the leather bindings on her books till I sneezed? Or maybe move in - permanently??)
Other movies which have a steam punk vibe also include Disney's Treasure Planet (wouldn't dare post a pic they'd probably sue me and take my house for violation of copyright) a Series of Unfortunate Events (who didn't love that closing credit sequence of illustrations??)
I don't think you could quite include Harry Potter although I think the Golden Snitch probably comes close - enchanted objects are too into the magical fantasy as opposed to something quite conceivably built by a mad scientist or creative genius.