[HumanDrivenDev]

Interlingua is the most intriguing conlang for me. It just seems incredibly practical. I'm a native English speaker with only high school french, yet I can pretty much read interlingua despite never having learned it. I imagine native romance language speakers are fluent readers right off the bat. That's huge.

[geowwy]

Folksprak is another one like Interlingua, except based on the Germanic languages. One of the nice things about being an English speaker is you can pick up both pretty easily.

Another interesting one is Uròpi which tries to go back to the Indo-European roots of all European languages. It's not as immediately readable as Interlingua or Esperanto but not too bad either: http://uropi.free.fr/comparaisons.html