It is usually desirable to keep the software installed on your computer up-to-date, but this is very difficult and time-consuming if you have many programs installed. Sometimes software will have automatic updates (such as Adobe Reader, Mozilla's Firefox and Thunderbird, Skype, iTunes, etc.), but this isn't true of all software. That's where Software Update Monitors are useful. A (sometimes) quick scan of your computer by one of these products will reveal which software is old and needs to be updated.
Secunia's Personal Software Inspector (PSI) is for those of you that are only interested in patching insecure software and do not require the updates that are not security related. It will let you know which programs are patched, which are insecure and which have reached their end-of-life. After it has scanned your PC, it can remain open in the background to keep an eye on any changes you make. It lists all your programs, and provides links to the vendor's homepage, technical details, the installation folder and "Add/Remove Programs". It also allows you to choose between informing you of easy-to-patch program updates only, or all updates. If it detects software that requires patching, it will provide a link to the download page. Unfortunately, it's in release-candidate (RC) stage, but it works well and I would suggest keeping an eye on this program.
FileHippo.com's Update Checker (UDC) is the fastest of the three and very easy to use, but detects only a limited number of programs. It scans quickly and takes you to a webpage that provides a list of the programs it detected and links to the FileHippo.com download page for the new software. It also allows you to decide whether or not to view Beta software. Although it's probably the best looking and easiest to use, it's very limited in what it detects. In order to improve its detection rate, you have to add your "Program Files" folder to its custom folder search and force it to evaluate all subfolders. This makes it slower, and it still doesn't detect all software; instead it detects only the software that's available on the FileHippo.com website. The advantage of this is that UDC informs you of software updates (after a scan) as soon as they become available, whereas the other programs occasionally show a delay in detecting updates. I would recommend this program to those of you who mainly use freeware available on FileHippo.com, feel least comfortable around a computer or want to be notified about every update that becomes available.
Another useful program is KC Softwares' Software Update Monitor (SUMo). It's faster than Secunia's PSI and FileHippo.com's UDC. SUMo also let's you decide whether or not you want to be notified about Beta software. However, one drawback about the program is that, even though I did not allow Beta versions, it still occasionally informed me that Beta or RC updates were available, and did not mark them as such. Another feature that you may or may not like about SUMo is the result you obtain by clicking on the "Update" link for new software. Whereas PSI and the Update Checker take you directly to a download page, SUMo takes you to a webpage with useage statistics about recent versions of the program, and displays the number of users who use each version. Although that may be interesting, there is no direct link to a download page. SUMo's page gives you links to three major download sites' search pages (which sometimes do not work with the information supplied by SUMo) and a link to a Google search for the software. The advantage of SUMo is that it informs you of updates to software that is not limited to security updates (such as PSI) or availablity on FileHippo.com (such as UDC).
Personal Software Inspector (PSI)
Website: https://psi.secunia.com/
Download Link: https://psi.secunia.com/
Author: Secunia
Current version: 0.9.0.1-B (RC1)
Version date: 2008
License: Free for personal use
Download file size: 475 KB
Operating systems supported: Windows 2000(SP4)/XP(SP2)/2003/Vista
Additional software required: None
64 Bit version available: Unknown
Portable version available: No
Other languages supported: German & Danish
Update Checker (UDC)
Website: http://www.filehippo.com/updatechecker/
Download link: http://www.filehippo.com/updatechecker/
Author: FileHippo.com
Current version: 1.022 Beta
Version date: May 2008
License: Freeware
Download file size: 148 KB
Operating systems supported: Windows 98/ME/2000/XP/2003/Vista
Additional software required: Microsoft .NET Framework 2.0
64 Bit version available: Unknown
Portable Version Available: Yes, available here: http://www.filehippo.com/updatechecker/
Non-English languages supported: None
Software Update Monitor (SUMo)
Website: http://www.kcsoftwares.com/index.php?sumo
Download link: http://www.kcsoftwares.com/index.php?download
Author: KC Softwares
Current version: 1.8.1.45
Version date: 20 April 2008
License: Freeware
Download file size: 1.04 MB
Operating systems supported: Windows
Additional software required: None
64 Bit version available: Unknown
Portable version available: No
Other languages supported: Many - see here.