Actually, if you're trying to just to the kinds of things that are easy on an ASPX page doing the extra few steps to make a module isn't that big of a deal. Run the template, slap your stuff in the generated view and edit pages, and you're pretty good to go. You could even take a basic module like SimpleArticle and use it as a template and update the names. There are serious advantages to being "inside" the DNN umbrella, like security and logging that you pretty much get for "free".
The iFrame solution is quick to a point, but speaking from experience it gets messy over time. I would only consider it temporary unless you plan to freeze the DNN version and underlying OS. I had a couple solutions I just ran in iFrames but then the inevitable OS upgrade happened, then of course I had to change some skins, and then I got some conflicts with what was inside the iFrame, on and on. While it's been work upgrading the DNN modules I wrote way back when, at least they kept working (for the most part) as long as I didn't recompile them. The iFrame stuff broke immediately.