Stackless Python is used extensively in EVE Online to provide cooperative multitasking. It allows tasks to be split across multiple tasklets that run concurrently without preemption. Channels are used to synchronize tasklets in a way similar to coroutines. This approach allows EVE's massive multiplayer server to handle over 120,000 concurrent users on a single database shard using Stackless Python's lightweight tasklets and channels for communication and synchronization.