Before uploading photos to a wikispace, website (or even an online photo storage site specifically to create a slide show) it is worth spending a few minutes resizing them.
Smaller photos are FASTER to upload and MORE MANAGEABLE once they are on the page/slideshow.
A good size for most wikis and webpages is 320 x 240 pixels but try a few and you will soon discover what suits you best.

This free online resizer is quick and easy to use to compress photos for the web

Resizing on a PC

Picture Manager

A quick and easy way to resize and compress photos on a Windows Computer :
  1. RIGHT CLICK on the picture you want resized - a window will open with an number of options
  2. choose Open With and then Microsoft Picture Manager
  3. when Picture Manager opens select Edit from the menu bar at top of page
  4. On the right of the page should now be a number of choices - choose Resize ( a good size for Wikis is 320 X 240)
  5. You can also Compress your photos here to make them faster to upload and download
  6. Remember to Save As when finished (by saving as rather than Save you retain the original photo in case you need them later)

Pix Resizer
Here is a free online application you can download from the internet -

free online tool resize, edit and crop one photo at a time in the one spot.

or ... this one resizes online and gives you back the resized photos via email (or sends them to a friend's email)

Photoshop Elements.
In photoshop Elements you can compress easily in 'save for web' file menu option. Here you can reduce easily using the % option.

iPhoto on Macintosh Computers will resize for you - simple select the photos you wish to upload, EXPORT them (to the desktop or a folder) selecting the size you wish them to be.

If you put a whole set of photos in a new album in iPhoto, or highlight a number, you can resize them all at the same time.
PHOTOSHOP ELEMENTS also provides simple resizing and compressing of photos. An option offered when you Save as is shown here:

You can also resize a number of photos at the same time in Photoshop by selecting Batch Processing from the File Menu - a handy tool!