Just released today is an add-in for Firefox that supports the auto-suggest feature in Live Search, available for download at Mozilla.org.

According to a blog post from Alessandro Catorcini, Lead Program Manager for the Live Search API:

This release, while relatively small in scope, takes advantage of the work we've done as part of our Live Search API 2.0 which enables the richest and most flexible search API offered by any major search provider.  We listened a ton to developers as we built 2.0 and the we think the feature set reflects that - multiple protocol support (in contrast to only AJAX from GOOG), unlimited queries for customer-facing sites and apps, and an awesome array of result presentation options. 

With this latest API release and the Open Search compliant RSS feeds that we've made available for all of our search content as part of Silk Road, Open Search clients will now be able to display query suggestions when using the Live Search API.

For developers, the new endpoint will serve Open Search query suggestions in JSON format (as they are consumed by major players like Firefox) and can be queried here.

Hmm, wonder what the Live Search market share is on Firefox?  Anyway, here’s some pertinent links:

Open Source Community at Microsoft blog post

Live Search blog post

Project Silk Road

Live Search API 2.0 Documentation