I usually make a separate class library for my projects and then break it up into folders

```
Services
 -all my .cs files that are service(business logic)

Data
 - Mapping 
   - nhibernate mapping files

Domain
  - domain files

```

I also create other folders like for instance I am doing stuff with foursquare so for all the `class files` for it are in a folder called `"foursquare"`

but what I don't know where to put `one off class files`. Like for instance I have `"HtmlWhiteList" class` what is the only kind of white list.

I don't think it should have it's own folder since it is just one file but at the same time I don't like just having it in the root.

Any suggestions where to put class files that don't deserve their own folder?