In addition to keeping a champion by champion skill list, I've also started working on a combination list of fun and useful things to try. Some of them require a full team but some of them I can do easily in solo queue.
List of team comps I want to try:
ADC / APC switch
The idea here is that a solo worthy ADC (Caitlyn, Graves or Ezreal) goes mid and the APC goes bot along with a support geared for them (Soraka, Morgana, etc). The goal is to take advantage of mismatched rune pages and mastery sets (mids sometimes don't take armor, for example) while also throwing teams out of their comfort zone.
Hyper Push
Against a team that's bad at pushing and, preferably, without an aggressive support
Top: Olaf / Shen
Mid: Sivir / Caitlyn, Nunu / Alistar
Bot: Jayce / Heimerdinger
Jungle: Alistar / Kayle
The idea being you switch have a semi-self-sufficient bottom lane that can survive while you push hard on mid with a hyper aggressive pushing combo and constant ganks to try to take mid. Then you switch and take top. At that point, top split pushes hard while you take down bottom. Then it's just a matter of continuing the rotation and applying constant pressure on the lanes. If the team gets a good kill of 2-3 key opponents, they take down the middle inhib. Otherwise, they just keep rotating to different towers.
Double Jungle
Aggressive jungler with a dedicated jungle support. Requires an ADC that can be sufficient but the goal is to let mid farm wraiths and basically spend the game in the enemy's jungle with frequent ganks mixed in.
Jungle: Janna (for speed and CC) / Alistar (CC and sustain) / Taric (CC and sustain) / Sona (speed and sustain) & Hecarim / Shaco / Xin Zhao
Bottom: Ezreal / Graves (self-sufficient ADC)
Top: Jayce
Mid: Akali / Ahri (champion with good damage and sustain)... also Kassadin, Katarina or LeBlanc as a possibility for mobility
Melee ADC
I think that support Anivia could work really well with a melee ADC. The wall traps people so that the melee can take down the enemy.
Bottom: Anivia & Darius / Riven / Fiora / Jayce?
Middle: Normal
Top: Jayce (so that we have a conventional ranged auto-attacker) or Kayle (Hybrid auto-attacker)
Jungle: Amumu, Hecarim, Malphite (someone with scary long initiates)
So a typical gank bottom looks like
Darius attack, Champions start to run, Anivia walls to split them and trap one. Darius attack, Darius attack. Wall melts. Darius pulls. Darius Ults. When the jungler gets involved, the Wall can be used to split and bait out a flash and then the jungler can come in with a stun/fear/knockup whatever and gank.
Support push Heimerdinger
Heimerdinger can be built 10/11/9 getting the following masteries:
CDR, AP, Magic Pen, tower damage
Health, MR, Armor, +30 health
Mana regen, 1 point in speed, Mana per level, 15% CDR on items
Take GP5 quints, armor seals, magic pen marks and AP glyphs
Rush Kage's Lucky Pick for the GP5 (and eventually Twin Shadows)
Rush Banner of Command... Use promote aggressively (with CDR on it, can be used once every 153 seconds. If you time it right, this lets you hit nearly two thirds of your minion waves with promote (you need to catch one near the base then catch the next one near mid line then skip one).
Then take advantage of your 15% CDR on items and get Deathfire Grasp, Twin Shadows, Zhonya's Hourglass and Shard of True Ice. At full build, that's a 39% CDR build with 363 AP and surprisingly tanky at 146 armor, 90 MR and the ability to go invulnerable for 2 seconds every 76.5 seconds (which, when you think about it, is nearly 3% invulnerability... that's a lot!).
Priority is probably Banner of Command, Boots (which, combined, only costs 3600) and then DFG or Twin Shadows after that. With this build, you probably never buy the Sightstone and maybe at some point you rush to a philo-stone into a Eleisa's to clear the slot. Taking heal + Clairvoyance and rejigger masteries if desired. You'll be a button pushing maniac but that's okay because Heimerdinger doesn't push a lot of buttons anyways (essentially hitting his Q when people are close and throwing his W when people scare him). Clairvoyance helps keep tabs on the jungle.
This seems like a great plan for practicing your map awareness as well as your 1-6 button pressing (something I routinely forget)
Support LeBlanc
LeBlanc / Urgot bottom lane: The goal is to get E early and harass with the landing of the E being a cue for Urgot to fire his DoT and then attack. A E/Q combo does 80 + 90 magic damage at lvl 2 with a 2 second silence and 3 seconds of 25% slow. Throw on a R / Q / Q combo from Urgot which should be doing 220 damage at lvl 2 and you have the vast majority of most champion's health. All it should take at that point is another Q or two from Urgot and/or some auto-attacks. Because the champion will be silenced, escape and/or retaliation will be difficult.
This setup needs to have Urgot farming for maximum affect but LeBlanc will almost certainly get some kills.
Shaco split pushing jungler
(key items are Statik Shiv, Boots of Mobility and then some combination of Zephyr, Warmog's, Phantom Dancer).
Darius Jungling
(building as a tanky jungler is probably best... So Spirit of the Ancient Golem, Sunfire Cape, Mercurial Scimitar / Maw of Malmortius / Wit's End??)...
Kill your carry, Irelia: Tenacious mastery + Zephyr, Warmog's, Trinity Force gives 85% reduction from CC in team fights. Unless they have knockup (Lulu, Malphite, Zyra), I'm pretty much unpeelable and unkillable. Additional items could be Spirit Visage (for massive amounts of mid fight sustain), Abyssal Sceptre (for MR tankiness and MR reduction), Guardian Angel / Aegis of the Legion for survivability or Wit's End / Phantom Dancer / Infinity Edge as situational. Mercurial Scimitar is also a possibility.