This is the most recent (and closest to final) draft of my Jund Ramp project. I've been working on it consistently for roughly three months and I've been having some serious success with it.
Works off of Cobra, obviously, but extends the Landfall ramp mechanic to include landfall breeding landfall, a la Expedition, which can lead to a Harrow, which then leads to Rampant Growth by floating mana alone. (Yes, I know Expedition only fetches two tapped. But you have to set one land to get to three, so even if it's a tapland you've got one floating before Khalni fetches.)
Potential to swing for 40+ by turn 5:
Turn 2: Cobra
Turn 3: Khalni Heart. Terramorphic/Fetch for two landfall, Harrow for an additional two. Khalni sets off. Total of 6 land. Two leftover floating, extra Khalni.
Turn 4: Set Fetch for 1 floating. Avenger of Zendikar. Fetch for first landfall. Seven 1/2 plants. Rampant Growth for another landfall. 2/3. Two counters on Khalni. Seven lands total.
Turn 5: Basic or tapland. Plants at 3/4. Khalni sets off. 5/6. [9 or 10 lands untapped, three floating. From here, assuming Avenger and Cobra are still alive, you're swinging for a total of 42. Seven 5/6 plants = 35, +5 from Avenger = 40, +2 from Cobra = 42. Not a bad turn 5. Follow up with your choice of Ramp/Harrow, Oracle, Comet Storm, Ultimatum, etcetera. Whatever you happened to draw into and have leftover mana for.]
Also, Lavaclaw, Comet Storm, Lavalanche, and Flameblast all make gorgeous use of the lands leftover from landfall. Late game, if you have a situation similar to the one described above, Flameblast can trigger for 10+ alone. I won't go in to talking about Ob, he's pretty self-explanitory.
"Why is Summoning Trap maindeck?"
6 mana is easy to get with this deck. The problem is, every now and then that game comes along where your fatties don't want to show up until you're around 5 life. Drop a summoning trap, and more than likely at least one of 8 different endgame creatures will be within the top seven. (Works out quite well for me.)
Vess also helps with this, if you have time to wait a turn on her tutor. Her stronger suit, however, is with Ob/Avenger and an Oracle. Tutor a fetch to the top, and voila. Two extra landfalls and a chance to shuffle.
--Sideboard--
Naturalize and Terastodon for O Rings and Journeys. 'Nuff said.
Gatekeeper for removal of protected creatures. (Shroud, etc.)
Doom Blade for non-black decks (swap with Terminate)
Extra Terminate and Bolt if Comet Storm isn't working out.
Lavalanche for weenie/Ally decks. (6 mana wipes the board of 3 toughness creatures and pokes for 3 to boot.)