If you're the recipient of the transaction, you can create a child-pays-for-parent transaction by spending the unconfirmed output in a transaction with a sufficiently high fee.

Your only other options appear to be to wait it out, or to get in touch with blockchain.info's customer support.

If you're one of the recipients of the transaction (i.e. via change output), you can create a child-pays-for-parent transaction by spending the unconfirmed output in a new transaction with a sufficiently high fee.

From what I hear, you can specifically select the inputs for transactions on blockchain.info, so it should be easy enough to craft a transaction to that end.

If you're comfortable doing so, you might want to try to export the private keys corresponding to the unconfirmed transaction and export it into another wallet in order to create a doublespend transaction to recover the funds.

Finally, you'd always have the option wait it out, or to get in touch with blockchain.info's customer support.

Note: I've never used blockchain.info myself, so please provide feedback to improve this answer if you have better insight.