Ask HN: Data sources for large scale real estate analysis?

I'm dabbling in real estate investments, especially in vacation destinations. I'd love to be able to do some targeted analysis on these markets, like average appreciation in value over a period of years and so on. However, access to this type of data is exceedingly difficult to find. I know that Zillow does have (sometimes) past sale prices, and if that's all I have to work with, I suppose I can try scraping that site. However, are there other sources of information out there you are aware of?

Again, I'm not making a business out of the data...it's for personal use. I'm just trying to make educated decisions.

Thanks!