Why? Isn't that what google code and sourceforge are for?
Good question. Sites like google code and sourceforge are meant to collaborate on software projects. The idea of the kettle exchange is to have a spot where you can easily drop fairly small utility transformation and/or jobs - things for which it would be a case of overkill to start up a whole new software project.
For example, many kettle users write excellent blogs to illustrate or explain a particular trick they are using. If they want to share their kettle files, they typically host it themselves. That's fine if you're comfortable with that, but if for some reason you can't or don't want to do that, you can use the kettle exchange instead.
How does it work?
How it works depends on what you are and what you want to achieve:
...users looking for a solution:
If you're just a user looking for a solution, simply browse the list of child pages, at the bottom of the page. The titles of the pages should offer you a sufficient cue to figure out if the page may be useful to you so you can read it. If you're lucky, the page will have a number of attachments, and hopefully the page will explain how to use those files.
If you have a similar tip to share, or if you want to thank the author of the page, or if you want to list a bug or put up a feature request, use the built-in comment functionality. Simply add a comment to communicate about the page with the author and the rest of the community.
If you see comments left by other visitors, please take some time to read those - perhaps whatever you want to say has already been said.
...contributors offering a tip or solution:
If you're an author, and you want to share some content, make sure you get a pentaho wiki account. Registration is free but requires an email address. With your accound data, log in to the wiki. You will then see a side bar on the left of the page. Way at the bottom, you'll see an "Add Content" link with a green plus icon. If you click that, you'll get a menu with an "Add Page" link. Click that to add your page.
When you added your page, you can write whatever you like. So please try to stay on-topic and write something about kettle that you wish to share with the rest of the kettle community. If you have any files you want to share, Add them by clicking the "Attachments" link, also in the left side menu.
Here's a few tips to make it easier for other community members to notice your contribution:
Pay attention to the page title. Use a compact but descriptive title that is completely on-topic. Avoid "funny" or "witty" titles - you can do that on your blog if you like.
Start your post with a very small section that summarizes everything. Author(s), License, short description, and Kettle version info is the type of stuff I like to put there. This will enable a visitor to immediately decide if they actually need to read your contribution, and this should make both you and the visitor happy since none of us probably has time.
Describe your attachments. If you have files to share, a little section that explains exactly what each attachment does, perhaps with an extra download link, will greatly increase the chances of your stuff actually being downloaded. Many people won't magically understand they need to visit the attachement link in the sidebar to find the actual downloads, so if you can make it easier for the visitors, you will increase the value of your contribution.
If you want to elaborate on your solution, save that for the bottom part of your post. Even then, try not to turn this into the next blogging platform. Rather, write your blog or in-depth article on your own blog or magazine or whatever, and use hyperlinks to connect the kettle-exchange contribution to the real meaty content.
If you have a whole bunch of related links to share, then it might be a good idea to conclude your contribution with a "See also" section where you list all the links worth visiting after reading your contribution.