First, let's clear up a misconception.
Armor Penetration gives you a constant %damage bonus, regardless of how much armor the enemy has see here.
It doesn't matter if your enemy has 300 armor or 15 -- penetrating 10 of that will have the same effect on total DPS increase.
That said, let's take a look at why Armor Penetration is preferred, even with its linearity.
Attack Speed is easy to acquire via items.
Armor Penetration is not.
You can more than match the effects of attack speed runes with a single dagger - 420 gold.
The cheapest item with Armor Penetration is the Brutalizer at 1337 total gold. By this metric alone, Armor penetration runes are worth approximately three times that of attack speed runes.
It is easier to use items to stack Attack Speed over Armor Penetration -- but to get the highest DPS, you want to stack both.
Given that the amount of Armor Penetration available via items is strictly limited, if one's goal is to achieve maximal values for both Armor Penetration and Attack Speed, runes for Armor Penetration are much better than that of Attack Speed.
Summoners Rift buffs:
Information applies to Pre-season 5 and can be subject to change
Granted by killing the Red Brambleback in either the Northern or Southern jungle.
- Basic attacks slow the target's movement speed by (8-15)% for melee attacks and (5-10)% for ranged attacks for 3 seconds.
- Basic attacks also deal 5-56 true damage over 3 seconds.
- Grants health regeneration bonus of 1% maximum health every 5 seconds
Granted by killing the Blue Sentinel in either the Eastern or Western jungle.
- Regenerates 25 mana per 5 seconds
- Regenerates .5% maximum mana (or energy) per second
- 10% cool-down reduction.
- Increases Max Energy (Cannot find source saying exact amount)
Both red and blue buffs last for 2 minutes without Runic Affinity and 2:24 minutes with it.
If slain, buffs held by the newly dead transfer to the killer.
- Grants up to 40 AD and AP scaling with game time
- Grants Empowered Recall reducing its channel time to 4 seconds. Successfully recalling will restore 50% of your maximum health and mana and grant 50% bonus movement speed for 8 seconds.
- Buffs all nearby minions and super minions (exact information can be found in the link).
Lasts for 3 minutes with or without Runic Affinity.
If slain, the buff is lost but not transferred unlike the blue and red buffs.
This is a permanent team-wide buff that stacks with the number of your team's dragon kills.
- Dragon's Might: +6% attack damage and ability power
- Dragon's Wrath: +15% damage to towers and buildings
- Dragon's Flight: +5% movement speed
- Dragon's Dominance: +15% damage to minions and monsters
- Aspect of the Dragon: Doubles all previous bonuses and your attacks burn for 150 true damage over 5 seconds, and also reveals the target for the duration. This stack only lasts 180 seconds.
Twisted Treeline buffs:
Granted by killing Vilemaw, the boss monster located at the top of the map.
- Bonus health regeneration
- Bonus mana regeneration
- Increased attack speed
- 20% Cool-down reduction
(No source can be found with exact details, but this unspecific info was found on the wiki)
Lasts for 2:00 minutes or 2:24 with Runic Affinity.
If slain, buff is lost and not transferred (same as Hand of Baron on Summoner's Rift).
One Altar
Two Altars
- +3 gold on unit kill
- Adds +10% attack damage and ability power
Capturing an altar will give +80 gold to all players on the capturing team and vision of the altar
Buff is permanent as long as you own the altar.
Altars first open at the 3 minute mark and are locked for 90 seconds after being captured. Once unlocked the other team can capture and lock it for themselves, but the same altar cannot be captured by the team that already owns it.
Crystal Scar (Dominion) Buffs:
- When walking over shrines, the player gains a 30% movement buff.
These areas are neutral, so both teams can utilize them.
lasts 10 seconds or 12 with runic affinity
- "It seems to give you 15 + 1.25 x level % of your champion's max health (Pending Testing.)"
- Add 2 points to your personal score
These areas are neutral, so both teams can utilize them.
Increased champion model size.
- A shield of 212.5 (+12.5 x level).
- Passively detonate a lightning blast inflicting 90 (+10 x level) magic damage on champion auto attacks and damaging spells.
This buff is granted to the first team to complete a "quest" on dominion.
50 seconds or 1 minute with Runic Affinity
Proving Grounds (ARAM) Buffs:
(Same as Dominion Health Relic)
- On both maps, it seems to give you 15 + 1.25 x level % of your champion's max health (Pending Testing.)
These areas are neutral, so both teams can utilize them.
FORMATTING TAKEN FROM @theorise
Best Answer
The cloud drake buff (Cloudbringer's Grace) reduces the cooldown on the transformation spells champions like Jayce, Elise, and Nidalee use, so it essentially functions as normal. It just feels a bit different because these champions naturally have low "ultimate" cooldowns.
As a special case, Udyr instead gains global cooldown reduction based on the number of stacks of this buff he has, equal to the amount he would normally get if he had an ultimate. Shyvana, whose ultimate is only accessible once she gains 100 Fury, gains additional percentage Fury generation from all sources based on the number of stacks of this buff she has.
Cloud Dragon Soul, which increases a champion's movement speed once they use their ultimate, operates normally on all champions except Udyr. As Reddit user phroxz0n, a Riot employee at the time, explains on this post, Udyr gains the additional movement speed from this buff on all of his spells, and is the only champion who currently does so.