IKNetworkActivityManager is a Cocoa class that simplifies work with UIApplication network activity indicator. It turns your networkActivityIndicatorVisible = YES/NO code to add/removeNetworkUser:, so you don't need to remember objects that can use network anymore. A demonstration App is available.
Jug is a task-based parallelism framework. Jug allows you to write code that is broken up into tasks and run different tasks on different processors. It uses the filesystem to communicate between processes and works correctly over NFS, so you can coordinate processes on different machines. Jug is a pure Python implementation and should work on any platform that can run Python.