I put together a summary of release dates for various tablets. Note this information is only specific to the US market. I know its not a complete list so if there are any that I missed, feel free to note and I will add if its good. Rumored tablets are excluded.
These release dates were obtained from various sources (company press releases, suppliers, news articles, other tech websites, etc). If there is an actual date (i.e. October 5, 2010), then it should be correct. The more general the date, the less reliable. Of course, these are subject to change without warning. We try our best to update these but encourage members to notify us if they have heard differently. We would then research further.
Sweet List to keep your eagerness in shape. Archos products and Stream TV EZ7 are already listed on some online retailers.