Which database(s) should I use?

[packo8]

I'm building an application that needs to query a lot of data that is written once and not changed anymore. Should I use MySQL for that or should I use something like SimpleDB or BigTable? (I need to write once, read many times)Thank you.Edit: I want to use Heroku, big for me is more than 5MB. "Thousands of rows" take more than 5MB. That's why I'm wondering if I should use CouchDB, SimpleDB or MongoDB in order not to pay the $15 that Heroku charges. Suggestions to overcome this? Thank you all for the comments!