How can I return an array of struct in solidity?

As you mentioned, this is not yet supported in Solidity. The powers that be are planning on changing it so you can, but for now, you have to retrieve the number of elements and then retrieve the decomposed struct as a tuple.

function getBidCount(bytes32 name) public constant returns (uint) {
    return highestBidder[name].length;

function getBid(bytes32 name, uint index) public constant returns (address, uint, bytes32) {
    Bid storage bid = highestBidder[name][index];

    return (bid.bidOwner, bid.bidAmount, bid.nameEntity);

Edit to address question in comment regarding storage vs memory in this case

Local storage variables are pointers to state variables (which are always in storage). From the Solidity docs:

The type of the local variable x is uint[] storage, but since storage is not dynamically allocated, it has to be assigned from a state variable before it can be used. So no space in storage will be allocated for x, but instead it functions only as an alias for a pre-existing variable in storage.

This is referring to an example where the varable used is uint[] x. Same applies to my code with Bid bid. In other words, no new storage is being created.

In terms of cost:

getBid("foo", 0) using Bid memory bid:

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getBid("foo", 0) using Bid storage bid:

enter image description here

In this case, storage is cheaper.

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