Hi Cypherpunk38 - this is actually in our API already (https://shapeshift.io/api.html#shift-conduit), you would use the following call for a normal conduit which would let you generate a deposit address:

url:  shapeshift.io/shift
method: POST
data type: JSON
data required:
withdrawal    = the address for resulting coin to be sent to
pair       = what coins are being exchanged in the form _

  ie btc_ltc
returnAddress    = (Optional) address to return deposit to if anything goes wrong with exchange
destTag    = (Optional) Destination tag that you want appended to a Ripple payment to you
rsAddress    = (Optional) For new NXT accounts to be funded, you supply this on NXT payment to you
apiKey    = (Optional) Your affiliate PUBLIC KEY, for volume tracking, affiliate payments, split-shifts, etc...

example data: {"withdrawal":"AAAAAAAAAAAAA", "pair":"btc_ltc", returnAddress:"BBBBBBBBBBB"}

Success Output:
    {
        deposit: ,
        depositType: ,
        withdrawal: , //-- will match address submitted in post
        withdrawalType: ,
        public: ,
        xrpDestTag : ,
        apiPubKey:
    }

Let us know if you have any questions on this but it should be what you are looking for.

Thanks for using ShapeShift!