reCaptcha has blocked me out of my website
If you can use SSH, or other shell, it's easy:


Install Drush. On Ubuntu, follow this document. Or simply unpack it and add it's directory to system's PATH variable (OS dependant).
Enter your Drupal's directory
Execute drush dis recaptcha


I strongly advise this approach, it may be a bit hard to set up initially, but drush is a powerful tool that can help you in future.

If you cannot, but you can use SQL client, it's not so bad too:


Login to your Drupal database with your SQL client
Back up your entire database
Execute UPDATE system SET status = 0 WHERE name = "recaptcha";


In both cases, you should be able to login, and uninstall reCaptcha module via UI to get rid of messed configuration data.