If I'm reading your question correctly you're asking more about the photo processing part of the problem (i.e. how to level out the differences in light, style, etc.) than the slideshow part (what software to use).

If that's the case I have a couple of suggestions that require very little in terms of software and know-how:

1. Picasa has a handy "I'm Feeling Lucky" button that auto-corrects the exposure of your photo and should also do a fair job of evening out the colour temperature differences between daylight, indoor and flash-lit scenes. If you're using a Mac, the Enhance tool in iPhoto does a similar job. Both also have a range of easy-to-use creative effects you can play with to apply similar styles to your photos.

2. If that still doesn't do the trick, converting to black and white is a great way to quickly hide all those colour and lighting imbalances.

3. Try cropping and/or adding a vignette (i.e. darkening the edges of the frame) to further reduce any background distractions.

4. Cropping to a standard size, and perhaps adding a frame, can introduce a running theme where there wasn't one before.

As a quick example, I took three quite different photos of my daughters and edited them the same way:

• Converted to black and white
• Increased the contrast a touch
• Close, square crop
• Added a thin black border

Do you think that comes close to the sort of consistency you're looking for?

Before

After