A combination of new users, increased interest, CryptoKitties etc has lead to a clogged Ethereum network. ICOs have also created quite a mess of the TX pool and has a lot of TXs pending and taking longer than normal to send.
If you have transactions currently being processed and not going through do the following:
Step 1. Cancel your current Ethereum transaction:
What is canceling: Generating a 0 ETH transaction to Your Own Address with the purpose of preventing a previous transaction from "going through" / "being mined" / being included in the blockchain.
Unlock the wallet you used to send the original transaction.
Don't change any fields. These are already filled in for you. If you change something, it will not work as intended, bad things could happen, and you have no one to blame but yourself.
Click the Send Transaction Button.
A dialog will appear. Click the "Yes, I'm Sure" button to send.
A new TX Hash will appear in the green bar across the bottom. Click the link to view it and see if you were successful. If it doesn't show up immediately, stop. Breath. Count to 20. Then click refresh.
Step 2: Create a new transaction and change the network you are currently on:
Step 3: Proceed to make the new transaction as normal
**NOTE: have a look at https://ethgasstation.info to see what the best gas price is currently.