If you need to share encrypted files regularly, we've shown you some of the best tools for the job before. However, if it's a one-off instance, Securesha.re can make encrypted file transfer dead simple.
The site encrypts any file you upload before it's sent to its servers, so you don't have to worry about it getting picked up during transmission. It then generates a self-destructing URL (all files are deleted after seven days) and password that you can send to your recipient. You can choose to send one big URL with the password embedded for simplicity or separate the file URL from the password. On the server end, the encrypted file is downloaded and unencrypted locally. No downloads or installations required.