crille

Non-ASCII characters can be used in the URL, but they have to be encoded (RFC3986). URL encoding is widely used (e.g. Wikipedia http://ja.wikipedia.org/wiki/Wikipedia:%E9%80%A3%E7%B5%A1%E5%85%88). 
This plugin encodes NON-ASCII characters in the slugs of your pretty permalinks. So your slugs may look like <code>fußball-in-nürnberg</code> or <code>連絡先</code>.

Permalink Encoding

This plugin encodes NON-ASCII characters in pretty permalinks by using Percent-Encoding described in RFC3986.

Aoirthoir

Converts plaintext URIs in posts or pages to clickable links. The Make Clickable plugin uses the WordPress make_clickable() function with an add_filter for the_content(). Install, activate and all of your plain text URIs will be clickable.

Make Clickable

Converts plaintext URIs in posts or pages to clickable links.

Permalink Encoding vs Make Clickable