You knew this was comming. You saw the Monopoly house rules thread. Here goes the Uno house rules thread. Lets include Crazy Eights Rules as well, but avoid all anarachy that Mao may bring.
All I can say is, make sure all people playing know exactly what the rules are, and how it works, and how it doesnt work.
Personally I don’t know any or play by any. I was in a couple games with UNO house rules, and well, confused and lost puts it nicely.
My family will switch seats every now and then, so that the same people are not sitting next to each other all evening. Otherwise, we tend to get a bit too vicious towards the end.
Our version of Uno is unofficially called “Screw Your Neighbor.” The only real rule we have that is different from the published rules is that if someone throws a Draw Two card, and the next person also has a Draw Two, they can throw it, causing the next person to have to draw four cards… unless he/she also has a Draw Two card, in which case the next person has to draw six cards, and so on. This can (and has) result in the first person having to draw as many as ten cards. It also makes people want to hold on to their Draw Two cards for such an occurance, which makes the points add up real fast if someone goes out.
The group I play by uses that rule too, LifeOnWry, and Draw Fours likewise accumulate.
That’s the only nonstandard rule we have for actually playing, but we do have a fairly elaborate scoring system for determining who the overall winner of a whole semester-long series of games is.
The variation we play is called “Stack.” Similar to what’s been described with the Draw Twos and Draw Fours, only with more options regarding how many colors, suits and numbers you can play. Stack is a pretty good game, mves the game quickly.
Let’s say the first card on the table is a blue 6. In your hand, you have sixes of yellow, red and green. You can “Stack” your red 6 > yellow 6 > and green 6 and leave whatever color suit you like on top. You’d have played three cards instead of one card on your turn.
OR, let’s say you have a blue reverse and a red reverse and the same sixes. Well, if you stack the two reverses, blue, then red, you reverse in one direction, then reverse back to yourself and you can play the red 6, yellow six and green six. You’d have played five cards on one turn.
You can play some outrageous combinations of stacked reverse, skip, and number cards using this method.
Each player can only stack one “Draw” card at a time, even in a two person game. When you stack the “Draw” cards, be it Draw Twos or Draw Fours, whoever’s caught short is SOL and has to pick up however many cards have ben played. The worse one I saw was 26 cards. LOL.
With stacked Skip cards you can skip consecutive players per card. If you have two skip cards, you skip the next two people, three skip cards three players, etc.
You’ll never play regular uno again.
Fast Uno:
Number of cards dealt each hand varies. When its your turn to deal you can deal any number of cards you wish.
You can play out of turn if you can match the last card played exactly (same color and number).
You can play two or more cards at once, if they are all the same color and number.
Draw Fours can be stacked.
You must draw four cards if you are caught with one card but didn’t yell Uno!
That’s very similar to a variant that my friends and I used to play in college, which made the game MUCH more fun. Basically, if you have multiple cards of the same rank (but not necessarily the same color), you can play them all as a group, as long as the first one you play would be a legal play for you. The last one you played is then left on top as the card the next person plays on.
Note, however, that you can NOT “go out” with a “stack”, because there has to be a chance for someone to catch you forgetting to say “Uno”. So if your hand is 5 8’s and nothing else, you can play 4 of them at once and say “Uno”, but not all 5.
With skips, this means that you can skip all the other players at once, even in a non-2-player game. If there are 4 players and you have 3 skips, red green and yellow, and a green 6, and it comes to you with a yellow card showing, you can play yellow skip-blue skip-green skip as a group, say “Uno”, then immediately play green 6. So it’s possible to just “go out” with no one else having a chance with skips (or, in a 2 player game, reverses), but not with just numbers.
With draw 2s or draw 4s, we also used the rule mentioned here were the person who would be drawing can play more of the same card to send the drawing forward. This leads to some interesting strategic choices. For isntance, if it’s just me and one other guy, and my hand is 2 draw-2’s and one other card, in normal uno, I’d auto-win (assuming the colors matched up right) by playing draw 2, then draw 2, then say “Uno”, then my other card. With stacks, if I am certain that my opponent has no draw-2’s, I autowin by playing my 2 draw-2’s as a stack (making him draw 4), then playing my other card. However, if I suspect he has a draw 2, I play my first draw 2 hoping to bait him into playing his draw2 on it, so I can then play my OTHER draw 2 on that. However, if he didn’t have any draw 2’s, me might draw one as one of his 2 cards, so my plan might backfire. Etc.
It’s WAY more fun than normal Uno.
As for scorekeeping, if we had 5 players, we’d start with all 5 players and play until only one person was left with cards. That person would be out. The other 4 players would then start again and play until someone is out. Repeat until only 2 people are left. They play. The winner of that then gets one “point”, and we start over again with all 5 players.
Lacking Uno cards, we’d usually play something along the lines of:
2 = draw 2 (duh)
4 = draw 4 wild (again, duh)
J = Reverse
Q = Skip
K = Wild
If we really wanted to drag out the game, we’d add in the “draw until you get a playable card” rule, but usually we just draw once ('cause we’re too lazy to shuffle the deck).
Every time I play Uno, I always pitch my “additive” rule – the ability to place two cards that add up to the number needed. For instance, you could play a 6 and a 2 on an 8, or 2 and 3 on a 5. A variant on the rule would allow you to play a blue card and a yellow card to match a green.
Nobody will accept my rule, however. 
Fun trick: sneak the Wild Draw Four cards out of the Uno deck and put them in Magic - The Gathering decks. They won’t know what hit 'em!
The only way to play Uno in a large group (say, more than 4), IMHO, is with the rule that if you have a card identical to the upcard, you can play it, and then play continues as though you had just taken your turn.
This keeps everybody alert and paying attention, even when it’s not their turn.