Since the ICO craze started which are often badly designed we now have the actual need to see unconfirmed transactions.
With Geth you can use eth.pendingTransactions from the console (geth console or geth attach to an other running Geth instance. This will return all unconfirmed transactions sent from on of the local accounts.
If you want to see all unconfirmed transactions you can use an external service such as Etherscan.
I don’t think this feature is implemented in any of the clients yet.
With a blocktime of 15 seconds the amount of unconfirmed transactions, at this stage in the network, is just never large enough to warrant showing these statistics.
If you take a look at the Ethereum Network Status page you can see that each block holds about 2 or 3 transactions meaning that is probably the amount that was unconfirmed at one point.