AdamH Card Ratings
AdamH holds card ratings for all Dominion cards; the ratings are always open to input and data is compiled periodically. The poll is available here, and a summary of the results of these polls when they are compiled can be found here.
The current ratings were compiled from a sample size of 63 entries and the possible ratings for each card are 0-10. The spreadsheet containing the raw data and statistics on that data can be found here.