If you know about the Anne Rice addon, you will understand this one. It searches for a text in your newsitem and replace it with another text. The difference is that it does this on the fly when building news instead of when saving a specific newsitem.
The benefits of this is that the newsitems data is unchanged so you will not experience any problems when editing a newsitem. You can also apply a search-and-replace on all old newsitems without needing to editing them first. The cost is speed, but I have done some benchmarking and the loss in buildspeed is neglectable as far as I can tell. Any feedback and testimonials on this is much welcomed.
The addon has some additional features, and that is that you can specify that a search-and-replace should be executed for a specific news field, not just the Text-field. For the advanced user there is also an option to use Perl's normal regular expressions metacharacters.