Recently my dailies asked me to win 5 times as a Druid, which is a class I haven't really played with yet. My card pool still isn't terribly expansive, so I decided to see what I could do with a commons only deck. I ended up with the below:
The principle is fairly simple.
> Drop lots of guys, the more the better (Murloc Tidehunter and Razorfen Hunter shine here since they bring a friend)
> Swing with them when you can to plink down the enemies health a little.
> Drop Savage Roar, give everyone +2 attack (including yourself) and strike hard before the enemy knows what happened.
And, hope to beat any AOE spells, but that's the life a rush deck leads.
Key Druid specific cards:
Power of the Wild: Either gives you a 3/2 for 2, or, +1/+1 permanently to your minions. Either option is solid depending on how many guys you currently have, can be like a mini Savage Roar.
Swipe: One of only 2 cards that cost 4 or more in the deck, AOE of your own to help your little guys punch through (you need to level your druid to at least 8 to unlock).
Starfire: 5 damage + draws a card. Similar to swipe, intended to smack an offending threat such as a taunter out of the way.
Other cards that tend to be especially useful (but not quite "essential"):
Abusive Sergeant: a 2/1 for 1, and gives something else +2 attack when he enters the field. That boost can regularly help a single small unit trade with a much larger threat.
Razorfen Hunter/Murloc Tidehunter: Since they bring a friend, they gain twice the benefit from a Savage Roar.
Argent Squire/Scarlet Crusader: Divine shield tends to make these units more time consuming to kill, and all going to plan time is something your opponent doesn't have. It of course also lets them eat a threat without dying themselves.
Outside of that, whatever you have should work fine. Just so long as they are aggressively costed/stat allocated. Don't bother with taunts, or creatures with a heavy emphasis on defence, it will only slow you down.
Faerie Dragons would probably go nicely, their non-targeting ability will make spot removal harder, but won't impact your buffs ability to beef them up.
Knife Juggler could also earn his keep nicely.
The deck has initially shown itself to go alright, although almost certainly not something you could go all the way up to legendary with. I'll take some video of a few games and upload.