Langwitches has recently updated his phenomenal post on the The iPad Apps for Bloom Taxonomy. This post has an awesome aggregation of iPad apps organized according to Blooms HOTS ( Higher Order Thinking Skills). If you are a teacher or educator and have not yet read about Bloom's Taxonomy then let me tell you that you are missing out on a great resource of educational insight. One of the most popular posts here in Educational Technology and Mobile Learning is Bloom's Taxonomy: The 21st Century Version. I recommend that you read it to have an idea of the importance of this taxonomy in education.
As for the the apps Langwitches has suggested for each skill, you will find almost half of them are not free but they are not expensive anyway. Below is a screenshot of the iPad apps taxonomy and you can click here to read the original article.