Here are a variety of achievement and proficiency tests for self-assessment online. They will give you insight and practice. There is always something to learn from these practice tests! 

The National Spanish Exam Information and Practice Site...always good for extra listening and reading practice, as well as vocabulary and general grammar. Remember to practice from previous years (all available at the following link) to prepare for the 2012 exam:  

http://www.nationalspanishexam.org/index.php/exam-preparation/past-examinations

AulaDiez (3 different level tests)

BBC Spanish Language Test (questions adapt to gauge student proficiency)

Don Quijote (5 levels from beginner to advanced)

LinguaWeb (Intermediate and Advanced levels with listening)

Transparent Language (grammar, vocabulary, and reading comprehension)