How to get different size image on views
I used IMCE under Drupal 6.x. However, the resize only occurs at the time you upload and image with their editor which is cumbersome, to say the least. It depends on who has to upload the images, I guess.

Otherwise, CSS, as others mentioned, is probably your best bet. Now a day, browsers properly (cleanly) resize images so they still look good. (10 years ago, however, it was horrible!)

If you want to use IMCE and need to resize existing images, you could look into using convert on your server to resize existing files. However, you'll have to write an intelligent script that properly renames everything properly...