I use Eclipse to code and I use Gimp 2.0 to draw the textures (You are going to need it if you are going to add any new Items into minecraft.

Notepad++

There aren't any special softwares to create minecraft mods. Modding is pretty much the same as coding. It's only text, text, writing, and more text. First of all you should learn how to set up mcp here: http://minecraft.gamepedia.com/Mods/Creating_mods
You can use a program like eclipse which can save you a bit of time when modding, but I recommend that you go through some modding tutorials.