I don't know about you, but I'm excited about OzCLO - the Australian Computational and Linguistics Olympiad. I only studied linguistics at uni for a year, but it was one of my favourite courses from my five years there. The competition only started in 2008 and aims to help students "to develop... strategies for solving problems in fascinating real languages."
The sample problems on the website are fascinating, dealing with a huge variety of languages including Aboriginal languages, Japanese braille and Linear B (an ancient Greek script). The problems are challenging, and encourage you to think analytically and creatively. I found them really stimulating, and can imagine that they would be perfect for gifted and talented students. I'd love to enter a team from my school for next year's competition - stay tuned to hear more.