There are different ways to use cloaking in SEO :
Invisible or Hidden text
Using this approach, webmasters add additional information like keywords stuffing, overwriting content in a way that is invisible or hidden to the users.
Flash Based Websites
As you know flash is not recommended as per SEO guidelines. But there are lots of websites that are built in flash only or that requires a lot of flash and they cannot avoid it.
Cloaking in E-Mail
In e-mail distribution, cloaking is the act of masking the name and address of the sender so that the recipient does not know who sent the e-mail.
HTML Rich Websites
A good SEO recommends to have “TEXT to HTML ratio” as high as possible. In other words, your web page should have more text (content) as compared to your html tags.
Image Gallery Websites
Image gallery websites have more images than the actual content on their pages. And images are not scanned by crawlers.
URL Rewriting
This practice includes the removing unnecessary parameters and other URL.
Replacement of Java Scripts
Using JavaScript to show content to non-JavaScript capable visitors that matches the textual information within a Flash.