We are very careful about recommmending pay-based sites. Heck, it's the internet and there're tons of free code and things to download.
But if you want to learn DotNetNuke, or keep up with what is going on, or have questions about how to use it, DNN Magazine by DNN Creative is the place you should subscribe to. It's less than 50 dollars a year (and no, I don't get a cut for recommending it, nor would I accept it), and there are already almost 200 videos, tons of tutorials and non-moderated forums for you to ask questions of other DNN users.
It's a steal, IMO. And as someone who has created interactive magazines, I know how much work must go into creating one that is successful and offers good value. Lee Sykes, the editor at DNN Creative has created an interactive magazine with video tutorials, written tutorials, module reviews and informative forums that passes this test with flying colors. So if you're interested in DNN, you need to subscribe.
One other subscription site, which is also less than 50 USD per year to join is Scott McCulloch's Ventrian Systems site. There are a number of handy modules here, and Scott has a great blog with lots of good information. Scott is also a member of the core team of DotNetNuke, so you know his modules avail themselves of the same excellent design that is evident in most of the DNN core.
Downloading just one of the modules, like the Articles module, or the Private Messages module, or any of the other modules Scott offers, all for either a 3 month subscription or a 1 year subscription (the last I checked, the one year subscription is 35 USD a year, of which one module, including source, is worth that amount). If you want to be able to inspect code, see how a DNN module should be built, Scott's site is the best place to go.
I promise, you won't be disappointed if you spend the money.