Here's Microsoft! From a recent ZDNet story:
Judge Kollar-Kotelly heard that total donations to political donations from Microsoft and its employees to political parties, candidates and PACs in the 2000 election cycle amounted to more than $6.1 million. During this period, Microsoft and its executives accounted for $2.3 million in soft money contributions, compared to $1.55 million by Enron and its executives for the same period.