The tutorials as live demos are great. You should say "live demo" somewhere, because "tutorial" makes it sound like text.

The front page is a bit split-personality: you have the idea of data mining; and the idea of sharing data sets. I think you should pick one to be the dominant focus, with other one present as an aside. It might make sense to focus on producers at the beginning ("scrape data and share it"), and once you've built up datasets, switch the emphasis to consumers ("wikipedia of datasets"). Maybe it's worthwhile to check how similar producer-consumer websites did it at the beginning: wikipedia, youtube, flickr.

BTW: What do you think of an interface like excel has for web-scraping: it displays the webpage, and you select the bit you want visually (no coding, not even html)?