A crowd-funded donation wallet with a minimum cap. All ETH is returned to contributors if minimum cap not reached. All funding passed onto payee. Multiple authorizers allowed.

JustGive.sol

pragma solidity ^0.4.10;

contract SimpleAccessControl {
  address public creator;
  mapping authorized(address => bool);
  
  function AccessControl () {
    creator = msg.sender;
  }
  
  function authorize (address entity) {
    authorized[entity] = true;
  }
  
  function deauthorize (address entity) {
    authorized[entity] = false;
  }
  
  modifier isAuthorized {
    if (true != authorized[msg.sender]) {
      throw;
    }
    _;
  }
}


contract JustGive is SimpleAccessControl {
  // start time
  uint256 starTime;
  // end time
  uint256 endTime;
  // min. ETH to raise
  uint256 minCap;
  // fund destination address
  address payee;
  // contributions
  mapping contributions(address => uint256)

  function JustGive (
    uint256 _startTime,
    uint256 _endTime,
    uint256 _minCap,
    address _payee
  ) SimpleAccessControl()
  {
    startTime = _startTime;
    endTime = _endTime;
    minCap = _minCap;
    payee = _payee;
  }
  
  // check that funding period is active
  modifier fundingActive () {
    assert(now >= startTime && now < endTime);
    _;
  }

  // check that funding period is over
  modifier fundingEnded () {
    assert(now > endTime);
    _;
  }
  
  // check that funding was successful
  modifier fundingSuccessful() {
    assert(this.balance >= minCap);
    _;
  }
  
  // check that funding was NOT successful
  modifier fundingNotSuccessful() {
    assert(this.balance < minCap);
    _;
  }
  
  // pay out contributions to payee
  function payout() external
    isAuthorized
    fundingEnded
    fundingSuccessful
  {
    payee.transfer(this.balance);    
  }

  // get refund of contributed ETH
  function refund() external
    fundingEnded
    fundingNotSuccessful
  {
    msg.sender.transfer(contributions[msg.sender]);    
  }

  // default function - contribute
  function () payable 
    fundingActive
  {
    contributions[msg.sender] = contributions[msg.sender] + msg.balance;
  }
}