PlantUML is another excellent UML drawing tool. With a text description of your UML, it will provide a diagram.
Really useful for sequence diagrams. For example the following easy-to-read code …
@startuml title Click & Collect hide footbox actor User mainframe Sequence Diagram User -> Web: Reserve Item Web -> Store: Check Stock Web <-- Store: Stock Levels alt Stock Available Web -> Store: Reserve Stock Web <-- Store: Stock Reserved User <-- Web: Reservation Number else Stock Unavailable User <-- Web: Out of Stock Error opt Special Order User -> Web: Customer Special Order Web -> Store: Order Stock Store -> Warehouse: Order Stock Store <-- Warehouse: Delivery Number Store -> Store: Allocate Inbound Stock Web <-- Store: Order Number User <-- Web: Customer Special Order Number end end @enduml
… produces a sequence diagram:
Just copy the above code into http://www.plantuml.com/plantuml. There are various ways to use PlantUML - not just via an online server.