KavaServices adds commands to the Services menu that let you:

• Translate text back and forth between several languages
• Search websites like Google, Wikipedia, Yahoo! and more
• Encode special characters into HTML entities or URL links
• Calculate mathematical expressions
• Convert currencies and other units
• Sort lines and remove duplicates
• Convert to lowercase, uppercase or title case
• Convert accented characters to plain ASCII text
• Calculate MD5 and SHA1 checksums
• Execute terminal commands

These commands will replace the selected text in any Mac OS X application, just like magic. You don’t need to switch to a different program, or even copy and paste. For example, you can even translate part of a web page or an incoming mail message.