Since there hasn't been a lot about Austrian dialects so far (at least from what I've seen by briefly skimming through the other comments) I thought I could shed some light on the Austrian dialects. Though I don't know a lot myself and am basing my knowledge on the fact that I'm Austrian and my own experiences, so feel free to correct me ^^

Someone said the Bavarian dialect and Austrian dialects are quite similar, that's not entirely wrong but for me I feel that it only applies to the northern Salzburgian dialects, so basically the ones at the German border. Apart from a few words and a slight accent my bavarian friends and I can understand each other without any problems and have a similar dialect. However the farther you get away from the German border (especially getting near the Alps) the dialect changes and for example my moms dialect (she's from a small village in the mountains), when talking with her relatives, is sometimes already hard to understand for me. It's the same with Tirolerisch and the other dialects which developed more secluded (like in valleys). Dialects from upper and lower Austria aren't too different from the Salzburgian dialect, some words are different and the accent too but in general they are quite easy to understand (for me at least).

So I guess the more secluded the area was while the language developed the more 'extrem' their dialect is. But every Austrian village or city has it's own variation of a dialect again ^^' sometimes it's more extrem and sometimes you don't notice anything. Maybe there are some language examples on youtube so if you're interested try searching for: Vorarlbergerisch, Tirolerisch, Kärntnerisch, Wienerisch, Sazburgerisch, Oberösterreichisch, Niederöstereichisch, Burgenländisch