vSphere has integrated NIC teaming capabilities. To utilize NIC teaming, two or more network adapters must be uplinked to a virtual switch (standard or distributed).
The key advantages of NIC teaming are:
- Increased network capacity for the virtual switch hosting the team.
- Passive failover in the event one of the adapters in the team goes down
There are various NIC load balancing (e.g. based on originating port, source MAC or IP hash) and failover detection algorithms (link status, Beacon probing) in vSphere, for details refer to: http://bit.ly/16Sm1ll

The maximum number of supported (and teamed) adapters per host varies by vendors and speed (max 32 for 1Gb and 8 for 10Gb)

New in vSphere 5.5. is the enhancement of the LACP capabilities.
The enhanced link aggregation feature provides choice in hashing algorithms and also increases the limit on number of link aggregation groups (22 new hashing algorithm options, 64 LAGs per host and 64 LAGs per VMware vSphere VDS, new workflows to configure LACP across a large number of hosts via templates)

Added in 5.1 was the Link Aggregation Control Protocol (LACP) support - which is a standards-based method to control the bundling of several physical network links together to form a logical channel for increased bandwidth and redundancy purposes.
LACP enables a network device to negotiate an automatic bundling of links by sending LACP packets to the peer. As part of the vSphere 5.1 release, VMware now supports this standards-based link aggregation protocol.