Avast Antivirus Home Edition (Free for non-commercial, home use!)
   Everyone should have an Antivirus program, and keep it updated religiously.  The folks at Avast have been providing the free Home Edition for years, and it includes Real Time Protection, and shields for E-mail, Instant Messaging, Peer-to-Peer downloading, network traffic, and internet pages.  The program also included integrated anti-spyware and anti-rootkit capabilities, and updates automatically. Avast issues updates on a daily basis.  The program is NOT a resource hog, i.e., it will not bog down your computer.  I highly recommend it.

AVG Antivirus and Avira Antivir Antivirus also provide free versions of their software, and of course you can purchase the "Big Name" products (Norton, McAfee, etc) just about anywhere.  Note also that many broadband internet providers (Comcast for instance) distribute free or extremely discounted versions of security packages that include antivirus, anti-spyware, and firewall software. Check the home page of your internet service and see!

Spywareblaster (Free!)
  The folks at Javacool Software have been producing this totally free application for years now.  Spyware, adware, browser hijackers, and dialers are some of the most annoying and pervasive threats on the Internet today. By simply browsing a web page, you could find your computer to be the brand-new host of one of these unwanted fiends!  SpywareBlaster helps keep your system secure, by preventing the installation of ActiveX-based spyware and other potentially unwanted programs, blocking spying/tracking via cookies, and restricting the actions of potentially unwanted or dangerous web sites. Unlike other programs, SpywareBlaster does not have to remain running in the background. It works alongside the programs you have to help secure your system. Simply install the program, enable the protection, and close it.  Then, check every other week or so for an update, as Javacool typically releases two updates per month.  Simple.  If you want to do automatic updates, they request a $10/year contribution. 

SuperAntispyware (Basic version free!)
  I've tried many anti-spyware programs, and I consider this one of the best.  I personally have the Professional version (which includes full-time protection), but the free version works great, and unlike many other "Free" anti-spyware programs, will actually ~remove~ the spyware, not just tell you about it and then tell you need to shell out however many $$$ to remove the bad guys!  
Note that if you provide your email address (which they do NOT spam with), you will get a pretty sweet discount on the purchase price after a few days).

Mailwasher Pro (not free, sorry)
  If you use a web-based email like Yahoo, AOL, Gmail, or the like, then you don't need this.  However, if you use Outlook Express, Outlook, Windows Live Mail, or any other "POP"-based email client that downloads the email to your computer, then I highly recommend this program.  Mailwasher allows you to view your email before it gets to your computer - so you can see what email is waiting for you so you can deal to it effectively and safely. The program will automatically import your email accounts.  Then, you simply check your mail with Mailwasher, and lists the messages on your email server.  The program evaluates the senders against spam databases (if you choose to have it do so) and lets you easily add your friends email addresses (or entire domains) to the friends list.  You can just as easily add bad email addresses or domains to the blacklist.  MailWasher Pro learns and adapts to your personal preferences by letting you teach it the kind of email you want to receive.  Good emails are colored green, and bad emails are colored red.  You can then choose to delete the email the emails you don't want, and then the program will open your regular email program and download the email.  Believe me, after a short amount of time, you'll wonder how you ever managed without it!  It's well worth the one-time price for the program.

Roboform (not free, sorry)
  If you're like me, by now you have dozens of website "logins" that you need to keep track of.  Some use your email address, some use a "User Name", and some require all kinds of ridiculous passwords.  Who can keep track of all this stuff?  Even if you tend to use variations of the same password(s) [which we all know we're NOT supposed to do!], it becomes an exercise in frustration trying to remember "which" variation you need! Roboform takes care of this.  It remembers the Site URL (address), login ID, and password for you, and when you come back, will fill in the form for you.  If you shop online a lot, Roboform can also fill in your name, address, phone, and credit card info (based on what you enter into your profile - you don't have to put credit card info in).  You can protect all of the logins with a Master password, and there is even a "mobile" version that fits onto a USB thumb drive.

X-Cleaner (Facetime has announced they are not supporting X-Cleaner any further)
  X-Cleaner is the swiss-army knife for privacy minded consumers.  This one-file application, which can be placed onto a thumb drive, can quickly scan for spyware, and do an in-depth scan if required.  X-Cleaner is particularly good at detecting "Trojans" placed on your computer that are intended to snoop out passwords and online activity. The program also has a number of useful utilities like a quick listing of all the items that Windows automatically runs when it starts, and the ability to remove them from starting with a double click.  The program can also shred files permanently to military standards, and perform system cleaning of recent activity.  It's one of the first tools I reach for when someone asks me for help, and says their computer is dragging!