Sorry about the English: my French is still horrible! (I'm Brazilian)
OK: you're looking for a free site where you can write an entire sentence in English and be able to hear.
http://translate.google.com.br/...|en|
At first, it is a site for translations - but if you set BOTH LANGUAGES to, for example, English, they will repeat exactly what you wrote in... English! Some hints are about punctuation: if it's too fast, you could insert commas between the words, or even periods, to make it even slower.
It's not a GREAT site for translations (though good), bur just perfect for pronunciation, as I just taught you.
Hope it really helps you! And I also hope to hear from you!!! (Why not?)
Bye!
Alice
PS: in case you need any other details, don't be afraid to write me, OK? I'm learning French and I know how hard a time it is... alice.amaral@uol.com.br We might even be epals (do you know what that is?? Rssss)