Earlier today I started working on a project that should make updating Windows Phones via cabs easier. It's called EasyWP7Updater. Currently only manual cab sending is enabled, you can grab cabs from the official update list thread or if you have a custom rom, your rom author might offer customization cabs.
Bug Reports and Feature Requests: https://github.com/jessenic/EasyWP7Updater/issues
Source code: https://github.com/jessenic/EasyWP7Updater/tree/
Future homepage: http://jessenic.github.com/EasyWP7Updater/
Please test and report all bugs you might find either responding to this thread or by posting them on the Issues page on Github. Feature requests are also welcome.
In the future I'll allow ROM builders to add cabs in the app, stay tuned!