notepad++ as editor
then start to look at how a little addon is done.
I could recommand few of mine per exemple, like
TheRollingTelVarStones . it's not very long or complicated and a good start. you have events, libraries and hooks inside it.
+ the wiki, other things.. if you need dev tools, look on the dev sections, there is few ones, i also made a little compilation of few ones, zgoo (data analizer) is interesting to have. or others which does same things.
ps: try to create something new, there is already tons of addons redoundants.