Orkut has disabled Right-Click option for security reasons. That means you can't just Right-Click and do a "Save Image".
To overcome this, most users have adopted a very crude method. Taking a printscreen, pasting it in image editor (like mspaint) and saving the required image portion.
The only drawback here is...there are chances of losing the crispness (image quality) when you save it.
If you really want to download the images in the actual form (high quality), here are few tricks that can come handy.
1) Click and Drag: The easiest and the quickest way to download an Orkut picture is to Click and Drag. Go to any image you wish to download. Left-Click the image and without lifting your finger, just drag the image to your Desktop. The picture will instantly get saved.
2) Drag to Address Bar: Incase the above method does not work, just drag the image to the Browser Address bar. This opens the individual image in the Browser. YOu can then Right-Click and save it to you Desktop.
3) Download entire Page: Go to Orkut Album. Click on a snap to enlarge...then goto File > "Save Page As". Once you save the page to your desktop, just browse the content of the page folder on your Desktop. You will get the required image in the Folder.
4) Using Java Script: You can use a code from Orkutplus.net to download images. You can get the code here (http://www.orkutplus.net/save-images-from-album.txt). un this code in the Orkut album page. You will be redirected to a page which will enable you to right click on the images.
5) Using Firefox: If you use Firefox as your browser, go to the image you wish to download. Go to the tools menu in Menu bar. Click "Page Info" > "Media" tab. Here you will get list of URLs cached in your temp files. Check the Preview for the required Image and save it to your Comp.
I'm sure there would be users having some more tricks on this. Send in your enties and I'll publish them too.