There are also many different ways to an Underworld Speedclears -- Some faster, some slower, some more dangerous. However, overall, the objective remains the same. Everyone wants the Underworld endchest, and everyone wants it fast.

First and foremost, the part everyone cares about most, are the builds. Here are the builds I run for each part of the Underworld Speedclears.
Smites/Wastes SF Terra
[build prof=E/A shad=12 earth=12+1+3 ener=3+1][Deadly Paradox][Shadow Form][Sliver Armor][Glyph of Lesser Energy][Ebon Battle Standard of Honor][Radiation Field][Intensity][Death's Charge][/build]
For safety and consistency purposes for the less experienced, these skills also help in wastes.
[[Shadow of Haste], [[Stoneflesh Aura], [[Feigned Neutrality]
I posted a video on Youtube to show how to solo ice wastes quest without shadow of haste: http://www.youtube.com/watch?v=WasLolyvMwk
Pools SF Terra
[build prof=E/A shad=12 earth=12+1+3 ener=3+1][Deadly Paradox][Shadow Form][Sliver Armor][Glyph of Lesser Energy][Ebon Battle Standard of Honor][Radiation Field][Intensity][Death's Charge][/build]
Once again, for safety and consistency at pools, these skills are helpful, especially when not using a cupcake.
[[I Am Unstoppable], [[Dark Escape], [[Feigned Neutrality]
Pits SF Terra
[build prof=E/A shad=12 earth=12+1+3 ener=3+1][Deadly Paradox][Shadow Form][Sliver Armor][Glyph of Lesser Energy][Ebon Battle Standard of Honor][Radiation Field][Intensity][Death's Charge][/build]
Depending on you PvE ranks, these skills may or may not be beneficial variants.
[[Light of Deldrimor], [[Viper's Defense]
Mountain SF Terra
[build prof=E/A shad=12 earth=12+1+3 ener=3+1][Deadly Paradox][Shadow Form][Sliver Armor][Glyph of Lesser Energy][Ebon Battle Standard of Honor][Finish Him][Feigned Neutrality][Death's Charge][/build]
[[Death's Charge] is replaceable by [[I Am Unstoppable] based on personal prefence. Death's charge to shake off Charged Blackness aggro if needed, I am Unstoppable to kill them if needed
[[Intensity] can replace [[Feigned Neutrality] if one knows how to pop traps then quickly death's charge to a nearby dryder before they do any damage.
The Mountain SF Terra in itself is replaceable by another Ursan. This results in having the core group complete vale then head to slayer.
The benefits of having four SF terras, however, is that if one fails, a one conset run is still possible.
Permasin
Post-nerf Permasins rely more on degen than pure damage.
[build prof=A/Me shado=12+1+3 inspiration=12 deadly=3+1][Deadly Paradox][Shadow Form][Channeling][Spirit of Failure][Arcane Echo][Cry of Pain][Ether Nightmare][Radiation Field][/build]
There are many variants to the A/me Permasin build. Below are a list of commonly used skill variants. Attribute points may be taken out of inspiration into which attribute as needed. Some are for safety and consistency reasons, others vary because of PvE ranks.
[[Empathy], [[Viper's Defense], [[Wandering Eye], [[Shadow of Haste], [[Death's Charge], [[Heart of Shadow]
[[Spirit of Failure] is replaceable by [[Auspicious Incantation]. This is based on personal preference and should have minimal difference in speed.
Ursans
Because [[Ursan Blessing] is a cross-class skill, any profession 'can' be an Ursan.
However, it is commonly preferred that Ursans are 'non-squishy' or non-caster professions and carry a Mesmer secondary for stances.
Most common is the W/me, which is probably the most optimal choice -- For their high AI, Stonefist Insignia, and [[Signet of Stamina].
Rangers, Dervishes, Paragons are also usually acceptable, for they are classed as 'non-squishy', though they lack Stonefist insignia and [[Signet of Stamina]. Paragons have an advantage over the other non-squishy professions, since they have a hard rez, [[Signet of Return].
Elementalists Ursans are a rarer, but are equally good, with the right armor of course. With Grail of Might active, Elementalist's with Prismatic Armor can achieve 9 attribute points in each element, matching the AI of a warrior. They lack the Stonefist insignia and [[Signet of Stamina], but they have more energy.
The Ursan build varies depending on whether a Mountain terra is present or not.
Ursan Build
[build prof=W/Me strength=12+1+1 inspiration=12][Ursan Blessing][Ether Signet][Dwarven Stability][Physical Resistance][Mantra of Flame][Signet of Stamina][Resurrection Signet][Sunspear Rebirth Signet][/build]
Without a Mountain SF Terra, [[Mantra of Lightning] or [[Elemental Resistance] is very helpful, along with [[I am Unstoppable].
Variants include [[Sprint] or any other running buff to run faster when out of Ursan Blessing.
High energy and low energy sets are very important in keeping up Ursan Blessing when needed.
Finally, the monk build-- ever since multiple terraway started, some monks have been shifting away from [[Healer's boon] and [[Heal Party], because there aren't that many Ursans to heal.
I have been in many runs, and I've seen many variation of monk builds, mainly including [[Healer's Boon], [[Word of Healing], and even[[Blessed Light]
Some monk have even switched to Hybrid monks, with both Prot and Healing Spells.
However, because I know many prefer cookie-cut builds, below are some of the most common/efficient ones.
Monk HB
[build prof=Mo/E heal=12+1 divine=12+1+1][Healer's Boon][Patient Spirit][Dwayna's Kiss][Seed of Life][Healing Seed][Heal Party][Glyph of Lesser Energy][Resurrection Chant][/build]
Monk WoH
[build prof=Mo/Me heal=12+1+1 divine=10+1 inspiration=8][Word of Healing][Words of Comfort][Dwayna's Kiss][Auspicious Incantation][Arcane Echo][Seed of Life][Healing Seed][Resurrection Chant][/build].
There are many variations, and as long as they can keep 2-3 ursans alive, they should be fine.