Canon:

Digital Photo Professional

Update Pages:  EU :

Worldwide: www.canon.com  then click on Support at the top and choose your country and language. You will be asked to select your camera model and then be able to choose the latest update for DPP.  (you won’t need any serial numbers) 

Nikon:

Nikon USA have an excellent “Versions Page” with details of the latest versions of all Nikon software and links to the most recent updates: Includes View NX2, Capture NX2, PictureProject, Nikon Capture, Wireless Utilities and Nikon Scan.

Nikon Software Versions

Nikon also offer full versions of their free software, not just updates.   

Pentax:

Pentax Digital Camera Utility

Update Page

Choose the Downloads and Literature tab.

As with Canon, only updates are supplied.

Sony:

Sony Image Data Suite

Update Page:  EU :

This page will allow you to select your country and language, before choosing your camera model, and software to update. Not the easiest site to get around, try choosing your camera as the Sony SLT-A55 to bring up the latest version of the software.

Update Page: USA, Canada and Latin America

This is a better site - much easier to get around.
Use the drop down menu at the top left to choose your country and language. 

Commercial Software

Most up to date software has some sort of automatic update system built in, but if you want to check if your software is up to date, follow the instructions below to find out what version you already have. Then click Help again and look for Updates or Check for Updates. That will usually take you to the maker’s download page.

Adobe Photoshop:    help / updates

Adobe Lightroom / Capture One / Bibble / DxO:  help / check for updates

ACDSee : Help / Product support and resources

Updates to the version you have are almost always free, but an update say from V5 to V6 will have to be paid for. Some manufacturers don’t make that very clear. Also updates will only install if you have a licensed copy of the program already on your PC.