My favourite image viewer was Irfanview for several years. It can view pictures, crop, resize picture, create a slide show etc.
Couple of years ago, I adopted Picasa from Google. Picasa could organize pictures on your system like itunes did to music. It could create a slideshow while playing a background music. Most important feature is it can upload pictures on the Internet and create slideshows for the web. Last year in my rotary club , I presented the secretary's report as a picasa slide show with a Yanni piece in the background. It was an instant hit and got me outstanding secretary award in the district.
Photostory from microsoft was another nice software. It creates a movie out of pictures with a background music. When my wife Sanjukta presented secretary's report for the Innerwheel Club , I used Photostory to create it with some latin flute music.
A couple of month's ago I came across Fast Stone Image viewer. This can project a slide show on an extended display. I use my Samsung LCD TV as an extended display to my notebook. The presentation is very good.
When we started our new website, I told Susmita to cycle pictures to break the monotony of the website. She was curious to know how to do the photo editing. I told her about Irfan view, picasa etc. To get great effects, you will have to use Photoshop or some such software. Photoshop is really hard to master for amateurs.
Then, I came across a really cool piece of software Photoscape. You can do all kinds of stuff like put frames around pictures, round the edges, correct for backlight, stitch photos etc. I was floored by its abilities and simplicity of use. Susmita now uses this to give a facelift to the pictures in our website.
I have always believed that the good things in life are not expensive (like air, water and street food). It is absolutely true in case of software. All the cool pieces of software mentioned here are free (except Photoshop).