I’m going to be quick here: after years with an iPhone, I’ve switched to an Android phone. That switch came with one unexpected loss: the Lumina app.
The Lumina app is great. Not only does it have the text of the NET Bible, but it has the notes from the study Bible. And it is free.
There doesn’t appear to be an Android version (though if there is, let me know!). The website is available, of course, but my building’s WiFi is slow, and the site doesn’t seem to work all on my phone.
So for you Android folks out there: is there a decent free study Bible app available?
Not that I care both about good and about free. I’m a big fan of study Bibles—I have four or so at home, and plenty more I plan on spending money on. This is just for Sundays when I’m running late to church and don’t want to pack my Jewish Study Bible (or whatever) on my bike, but I want some extra commentary during Sunday School. (Also, as should be obvious from the fact that I was using the NET Bible, it doesn’t need to be the KJV.)
By Common Consent, a Mormon Blog 
I use Olive Tree Bible Study app. Bonus points for being cross platform with Windows, iOS, and Mac as well.
I like the Blue Letter Bible app for the wide variety of translations it includes. I particularly enjoy the column view, to compare side by side the KJV with another translation I can better understand.
It does not include any study guide of substance tho.
I’m only a casual user but like MySword. A variety of Bible translations are available as well as other resources.
I use Olive Tree for NRSV with Harper Collins notes. I use Touch Bible for NET. It has the TN, TC, and SN notes, and can show parallel KJV verses. That means I can read NET to myself in gospel doctrine but have KJV right there if I’m called on to read out loud :)
I have both Lumina (I have an iPhone) and Blue Letter Bible. The thing I like about BLB is it gives me access to the original text. If you tap on a verse then pick Interlinear/Concordance it will show you the verse in Hebrew/Greek, and it will list every word in the verse. If you tap on a word it will take you to a lexicon entry for that word, so even if one does not know the underlying languages it’s a useful tool.
I have the Jewish Study Bible (2d Ed.), the HarperCollins Study Bible and the Annotated Jewish New Testament (RSV) on my Kindle App.
I love Bible Gateway.
My favorite tool at Bible Gateway is when you go to a verse you can click a link to see that same verse in all the translations in their database (something on the order of 50). Comparing and contrasting that way is always an enlightening experience.