The following are some simple apps a beginner can build while trying out rails web application frame work.

Goals on the completion of any app -

1. Understanding and practice of rails concepts(Action controller, Routing, Active record - associations and Views)
2. General web application development(Java script, Ajax, CSS and database - they will be using mysql for now)
3. Getting into the habit of code reviews and iterative development.

For this task, they will build the views with basic rhtml and css and later they will move to haml and saas.

One Page application that allows some one to add some products to his cart.(for now say products are books) . The user details and books can be populated directly in the database. A book has title, description , price and a thumbnail image.

1. List all the books on one page with pagination sorted by the least priced first. Clicking on the title should expand the description inline.
2. Clicking on add to cart should add it to the cart. One should be able to see their cart.
3. Nice to have a simple login mechanism.

Create an online diary which allows some one to write some posts(private or public). Public posts can be viewed by others and they can comment on them. Users can be populated in the database.

1. Page where you can create a diary post. Post should have title, description and a flag indicating public or not.
2. List all the public posts on page sorted by recent one first. Others can view this post(expand inline or light box) and comment on them.
3. Nice to have a simple login mechanism.

Create a two page app which acts as if it is a simple twitter app. Users can be populated inside database

1. Should have a login page. After logging in one should see all the tweets(messages) from the people he is following(Nice to update this page with periodic updater). A text box on the top to enter your message.
2. A page which lists all the users and allows you to click on a link to follow them. The ones whom you follow should not have this link.

Write a two page application that allows you to create some products under categories and search through them. Categories can be populated directly in the db. (Categories are like Books, Phones, Computers etc.)

1. A simple login module(just have one user for now)
2. Page where you create a Product and add it to a category. Product has title, description, thumbnail image
3. Search page which allows you to search by title or description of the product. You should also be able to filter by categories.

No need for any indexing engine in the initial phase. Good to look at Sphinx or Solr later.