Subject specific apps

I just read something in edudemic.com in which the author said that too often people look for subject specific apps rather than the more general ones to utilize.  That is quite true but in math, there are certain subject specific apps I've had to look for.  For instance, when I teach conic sections, I want a graphing app that will allow the students to graph ellipses, circles, hyperbolas, and parabolas without having to rewrite them into the y = something format.  I actually found one,MathGraph from the iTunes store.  It allows my students to graph all the conic sections and they have a choice of orienting it either vertically or horizontally.  It also has a small quiz section for each type of conic section.  It also does lines, exponents, log and ln.  I like using this particular app for my Algebra II and College prep classes.
While surfing today I discovered this website:
 http://www.educatorstechnology.com/2012/08/the-top-educational-ipad-apps-every.html
It lists 100 apps for the iPad but it is divided into topics such as Digital learning, Blooms Digital Taxonomy, etc. The one for Blooms Digital Taxonomy lists suggestions of apps for each level from creating to remembering.  This is one I am going to explore in more detail over the summer when I have  bit more time.