I've tossed the files in a folder on my Dropbox.
The RuneQuest SRD is widely and freely available (grab it here in Microsoft Word format or here in a very nice PDF).
Back in 2001, they also made the Blood of Orlanth epic, fully updated for the RuneQuest 2 rules, for free. The blog post link with the announcement leads to a dead link, but Google is your friend.
Mongoose also makes two freebies for Legend (essentially a reskinned RuneQuest) available, too. Check out Beneath an Opal Moon and Spirit Magic for some extras to add to your game.
As far as Traveller goes, you can grab the original three black books of GDW Classic Traveller for free at RPGNow.com OR download the Traveller SRD in Microsoft Word format from Mongoose here. I haven't been able to find a version of the Travller SRD in pdf, so if anyone knows of a fan edit, let me know.
There's also a great fan site with more info on the "Foreven Sector," the Open Content, non-canon sector of the Traveller universe which is described in the Traveller Developer's Pack.
Also be sure to grab the Secrets of the Ancients campaign and the Pirates of Drinax campaign, both for Traveller. These are free, too, courtesy of Mongoose.
And, of course, there is the huge archive of Mongoose's house zine, Signs & Portents, which contain many add-ons and adventures for both systems.
Free gaming: hell yeah!
EDIT: Link & files removed on 2015-03-05. I figure if you haven't grabbed them by now, you aren't going to, and I need to clean up space in my Dropbox account.