Checking the Balance of Your Account
You only need your public wallet address in order to see your balance. It is not recommended that you access your wallet by entering your private key anywhere if you just want to check the balance or see incoming or outgoing transactions. The fewer times that you need to open your wallet, the better.
https://etherscan.io/. Paste your address into the search bar and it will pull up your address and transaction history.
https://ethplorer.io/ allows you to easily see token balances and transfers.
https://gastracker.io/. Paste your address into the search bar and it will pull up your address and transaction history.
You can also enter your address on MyEtherWallet's View Wallet Info page by selecting the "View With Address Only" option at the bottom. Note: This only allows your to view your balances, NOT access you wallet to send funds. Remember, you must have the private key in order to access your account.