There are HTML character codes that can be used that you can look up. Either of below works fine for me (Firefox even converted the first one for me automatically).
You can use the HTML URL Encoding Reference at w3schools to get the codes.
There's also bit.ly or tinyurl for all other linking issues, but those should be discouraged because most people do not know how to use them safely (people should use the safe preview to prevent being linked to malicious sites).
Just for the record, in bit.ly, simply at a "+" at the end of the url string to preview it (i.e. http://bit.ly/12ZMCw9+). For tinyurl, use the "preview" subdomain instead of the main site (i.e., http://preview.tinyurl.com/123xyz)