The growing adoption of cloud computing and the proliferation of Internet-enabled handheld devices are changing the services landscape. Given the abundance and the variety of Software-as-a-Service (SaaS) offerings, we propose, in this paper, a framework for SaaS provisioning, which relies on brokered Service Level agreements (SLAs), between service consumers and SaaS providers. A Cloud Service Broker (CSB) helps consumers selecting the right SaaS provider that can fulfill their functional and quality-of-service (QoS) requirements. Its Selection Manager component ranks SaaS providers by matching their QoS offerings against the QoS requirements of the service consumer. Furthermore, the CSB is in charge of negotiating the SLA terms - using a multi-attributes negotiation model - with a selected SaaS provider on behalf of the service consumer, and monitoring the compliance to the SLA during its implementation.