Services that compete with PayPal's transaction model include Amazon Payments, Square and Dwolla. While each has different functionality, limitations or additional features, they each provide an alternative way to move money.
Amazon Payments functions similar to a PayPal account. Users fund the account by direct transfers from a connected bank account or credit card, and can use it to purchase goods online on sites that accept it. Dwolla accounts function the same way, but users fund them only by direct connections to a linked bank account. The service allows for sending money directly to LinkedIn connections or Twitter followers, and can send thousands of payments out at once. Square provides a similar service, though it also provides hardware and software for smartphones or tablets that allows for a user to directly swipe debit and credit cards to physically receive payments.