Constructed Languages

Esperanto is the most widely-spoken constructed international auxiliary language.  Basically, it is an artificial language designed with the intent that other people from can communicate with each other in this international language.  It is apparently really easy to learn.  Here is a quote from the linked Wikipedia article:

The Institute of Cybernetic Pedagogy at Paderborn (Germany) has compared the length of study time it takes Francophone high school students to obtain comparable 'standard' levels in Esperanto, English, German, and Italian. The results were:

• 2000 hours studying German =
• 1500 hours studying English =
• 1000 hours studying Italian =
• 150 hours studying Esperanto.

It should be noted, however, that these figures can only reflect the respective learning difficulty of these languages for native French speakers. They should be compared to figures from other countries to allow for a more general perspective on the learning difficulty of Esperanto. It should be noted in the chart above, Italian would naturally be easier for French speakers to learn since they are both Romance languages, where German is a Germanic language, for example.

Another intriguing artificial language is Interlingua.  It is designed to be easy like Esperanto, but it is based more on Romance Languages.  Here is a video of someone speaking Interlingua.  If you speak a Romance Language you may be able to understand quite a bit of this.

Besides these, there are several other such constructed languages.