Being a language nerd, I'm of course interested too in so-called "artificial" languages (the term "constructed language" is currently en vogue). Linguist Akrina Okrent wrote a great book on the subject a few years ago. Some are just kind of interesting as cultural artifacts, like Klingon or Orth (the latter from Neal Stephenson's Anathem). Others have a specific purpose, like attempts to base their languages in symbolic logic and to eliminate all ambiguity, such as Lojban (see also relevant xkcd).
But of all of these, I'm most enamored with Esperanto.
First, I love its purpose. L. L. Zamenhof, its creator, was a Polish doctor living in the late 19th century. He dreamed of a language not tied to any national identity, and which would be universal. This of course means it would have to be easy to learn. He spent about 10 years working on it before releasing his creation. The result is a language that is indeed simple to learn, with no irregulars and no unnecessary quirks such as grammatical gender or overly-complicated verb forms. The name itself (while not coming from Zamenhof) is a testament to its optimism: it means "one who hopes."
The vocabulary is generally pulled from European languages (especially Romance and English, with some Slavic mixed in as well). It's rare, though, to see a word and not have it be clear what it means. A few common examples:
* Vidi, to see
* Skribi, to write
* Blua, blue (adj.)
* Doni, to give
* Kun, with
* Libro, book
* Ami, to love
Despite the Western bent to the vocabulary, it has also blown up in China, with that country's first Esperanto museum opening in 2013.
The grammar, meanwhile, is super duper simple. As I said, there are never any irregular forms of any kind, ever. Nouns always end in -o, adjectives in -a, and adverbs in -e. Verbs conjugate for tense only, and even then there's only 6 forms (including imperative and infinitive). Compound words are extremely common, and so it's very easy to build one's vocabulary. It's also common to take a single word and change its part of speech.
An example text (Article 1 of the Universal Declaration of Human Rights). From here, which includes same pronunciations.
Ĉiuj homoj naskiĝas liberaj kaj egalaj en digno kaj rajtoj. Ili posedas racion kaj konsciencon, kaj devus konduti unu la alian en spirito en frateco.
All human beings are born free and equal in dignity and rights. They are endowed with reason and conscience and should act towards one another in a spirit of brotherhood.
I had put together a more formal grammar, which is hanging out right here.