Q:

Grammar checking API?

Are there any APIs that check the grammar of a given string?  
If so can you give examples?

A:

After the Deadline does exactly what I need. 
http://www.afterthedeadline.com 
It works really well, most of the time. But it does miss some common grammar mistakes (e.g. your/you're, their/there/they're, subject-verb agreement problems, etc.). 

