Aside from manual or core service scripts consider the **PowerTools PowerShell option**, compliments of Dominic Cronin, or **Content Porter**, especially useful to set defaults field values.

**PowerTools 2011 has (a PowerShell Version of) Component Synchronizer**. Dominic Cronin created a PowerShell version of Component Synchronizer [branched within the PowerTools repository][1]. If interested in helping, definitely reach out to see how we can integrate this into the CME Extension.

**Content Porter** . <strike>I've yet to try it, but </strike>Content Porter 2009 SP2 has an option to `Synchronize content against Schema before importing`.

[SDL Live Content explains][2] importing items without their schemas may mean they "may not be valid against the Schema found on the destination Content Manager." 

But if you select `Synchronize content against Schema before importing`, Content Porter will attempt to:

- Reorder fields to match the [target] Schema
- Remove fields not present in the [target] Schema
- Add fields to items, "on the condition that the fields are optional fields, or have a default value, or both."

This handles the typical schema changes, which I've [outlined in this post][3].

**Update**: I describe [**Content Porter component syncrhonization** on TridionDeveloper][4].

**Update**: Core Service now includes synchronization options (search online or see the documentation).

**Warning**: any synchronization approach can lead to data loss. Be sure to back-up and test your approach in DEV before automatically changing components. *It's called PowerTools for a reason.* ;-)

  [1]: http://code.google.com/p/tridion-2011-power-tools/source/browse/#svn/branches/dominic%253Fstate%253Dclosed
  [2]: http://sdllivecontent.sdl.com/LiveContent/content/en-US/SDL_ContentPorter_2009_SP2/7DGH253HDJDJ884JJLLAPWWRSFDH3737388D4
  [3]: http://www.createandbreak.net/2011/10/tridion-schema-change.html
  [4]: http://www.tridiondeveloper.com/sdl-content-porters-synchronization-option