Networking servers, such as web servers, have been widely deployed in recent years. While developments in the operating system and applications continue to improve server performance, programmable network interfaces with local memory provide new opportunities to improve server performance through extended network services on the network interface. However, due to their embedded nature, programmable processors on the network interface may suffer from inadequate processing power when compared to non-programmable application-specific network interfaces. This thesis first shows that exploiting a multiprocessor architecture and task-level concurrency in network interface processing enables programmable network interfaces to overcome the performance disadvantages over application-specific network interfaces that result from programmability. Then, the thesis presents a network service on a programmable network interface that exploits the storage capacity of the interfaces to alleviate the local I/O interconnect bottleneck, thereby improving server performance. Thus, these two results show that programmable network interfaces can offset the performance disadvantages due to programmability and improve networking server performance through extended network services that exploit their computation power and storage capacity.