Open Source Software is definitely the up-and-coming thing.
Mozilla is an open source software group that has created:
Internet Browser: FireFox
Better than Internet Explorer, tabbed browsing, no popups, no spyware, security.
Email Client: Thunderbird
Better than Outlook, haven't used it yet but it definitely looks safer (its not integral with the Windows kernel like Microsoft programs are), and its ported to Mac and Linux as well!
Sun Microsystems headed up this one:
Office Productivity Software: OpenOffice.org
Definitely up there. I haven't used all the features yet, and its not complete yet. But it so far is definitely compatible with Microsoft Office, and a few other office suites as well (no compatability with Lotus Smartsuite yet).
One huge advantage of these softwares is that they are not integral with the kernel. One huge security risk for Microsoft Programs is that they function hand in hand with windows operations, so Microsoft has had a hard time patching security holes. These are written in an entirely different way, and since the source code is published on their websites, developers can check out the code themselves (and if you don't trust it, you can download the source and build your OWN software).