The following are plugins written originally for WP Single but have been modified to work with WPMU.

Most Recent Posts (Updated Again)

Sitewide Extended Categories Widget

LinkedIn hResume for WPMU

Xpert Mailer

MU - Advanced Admin Menus

Audio player for WPMU

lighter admin menus for WPMU

WPhone MU Edition

WMPU Ldap+CAS Authentication Plug-in

Search Pages

Farms comment spam pack

Embedded Video with Link MU

Most recent posts - updated

WP-PostRatings MU

Persistent Styles for WPMU

Sociable Plugin for WPMU

Swift-SMTP Mailer

WPMU Comment Timeout

Share This WPMU Edition

WPMU Livejournal Crossposter

Flickr Feeder

WP e-Commerce

Enhanced Links

Sitemap Generator Plugin for Wordpress(mu)

RS-Discuss

LDAP Authentication Plug-in

Auto Links Discovery Plugin

MU Admin Bar