As a software junkie with an accumulation of images I have tried a lot of tools over the years. Here are some that everyone should look at before picking a tool of choice. These all allow you to browse your images, do quick changes or batch changes. Some offer powerful tagging/organising/searching tools too.

Free

Image viewer 2 -  http://www.dimin.net/software/imgview2/ - a very nice image viewer with all standard features and tools. including browse, batch changes, plugins etc.

slow view - http://www.slowview.at/ - a simple image viewer with all standard features and tools. including browse, batch changes etc.

xnview - http://www.xnview.com/ -  image viewer with all standard features and tools. Lots of formats.

irfan view - http://www.irfanview.com - very well known image viewer/simple editor. Weak in the browse/organise. Lots of formats.

Commercial:

photocase - http://www.dolphinprod.com/photocase.htm -  complete tool, aimed mostly at people taking lots of digital photos. SOme very clever ideas. mac and pc. $20

ashampoo illuminator - imagie viewer, some editing. Registered version comes with nice screenshot tool and a slideshow maker/distribution tool. $39 but if you sign up on their mailing list you can sometimes get a special offer as low as 7.99

firehand ember - http://www.firehand.com/Ember/index.html - very fast, lots of features $39.95

imatch - http://www.photools.com/ - Image management tool. All the basics plus very good categorisation, rename i/o options,  $49.99

compupic - http://www.photodex.com/ -  view, organise, tweak, optimize, export. $29-79

Thumbs Plus - http://www.thumbsplus.com/ - Has been around as long as I remember. Creates a database of thumbnail and powerful search/keywords. Supports more than just images, also fonts, sound etc. All the functions you expect. $79.95