There are a ton of other non-canonical texts. (And just to clarify, the Dead Sea Scrolls are not "Gnostic" texts, as you might have implied, which is an appellation usually applied to the Nag Hammadi texts.)

You can find a pretty comprehensive list of them at http://www.earlyjewishwritings.com/ and http://earlychristianwritings.com/ -- though the latter definitely includes "Gnostic" texts as well (also, the proposed dating range for the composition of quite a few of these texts is long overdue for an update).

There are so many awesome texts out there!
I'm really partial to the character of Enoch, and the more weird, apocalyptic sorts of books. I'll throw a few of those out there for your perusing pleasure. I'm using two Wiki links to give a general overview of the two texts I'll talk about, but please

The Book of Enoch, or First Enoch - this book is regarded as canon by Christians in Ethiopia/Eritrea, but not by other churches. I think it is particularly interesting because Enoch is taken around on a grand tour of the cosmos: he sees the world, up into the heavens, and even down to Sheol. It's pretty cool to read how people reckoned the cosmos worked back then. There are weird visions of angels, a few parables and even an astronomical calendar text thrown into the mix.

Slavonic Enoch, or, Second Enoch is unrelated to First Enoch (i.e., different author, very different date and region) but contains a lot of the same sort of stories about good old Enoch. There's also some stuff about Melchizedek, whom you probably recognize since it seems you're interested in Gnostic stuff. (the Wiki link for this one isn't as strong as the first- please check out more sources for better analysis of the text)

More information on the books of Enoch:

Jewishencyclopedia.com

Detailed analysis by Andri Orlov

If you are looking for more fun Gnostic stuff to peruse, and haven't checked out Apocalyptic/Gnostic scholar Elaine Pagels yet, you're missing out: Youtube Discussion about the Book of Revelation I'd definitely check out her books on the Origin of Satan and Revelations