If your Bitcoin transaction is currently stuck in purgatory with no confirmations, what you can do to try and speed up the process is use a transaction accelerator like https://pool.viabtc.com/tools/txaccelerator/
This accelerator is run by a mining pool so they will attempt to put the transaction in the next block they mine (I believe as long as you attached a fee originally). However they place an hourly quota on the feature so you may get an error message which means they've met the quota.
You can also use http://confirmtx.com/ who will do it for free if the transaction size is under 500 bytes and for $4 if the transaction is over 500 bytes. They will refund your money if it's not confirmed within 12 hours (exception being if the transactions falls off before the 12 hours have elapsed or you double spend).
https://pushtx.btc.com/#/ charges a fee no matter what and will give you an estimate when you enter the transaction ID.
Those are the only 3 I have heard of, but have not used either of them yet, so I can't testify to their success. People have reported using the first one with success so your mileage may vary.