Requirement: basic MySQL, xHTML and PHP knowledge.

1. Create new field "source" in mySQl table (ie Articles)

2. Add new input field to your Article add/edit form

Open admin/templates/article_edit/form.xml in your favorite editor.

Add folowing code:

<div class="content_list_body_header_line1">
  Source: <input type="text" class="article_title" name="ARTICLE_source" value="{article.source}" />
</div>

Notice the name of input field ARTICLE_source (you need to use ARTICLE_your_field_name) and value article.source (also you would use article.your_field_name)

3. Add new field to your frontend template

Open templates/xhtml/article/default.tpl and add following code:

(<vte:value select="{article.source}" />)

after article title (or whereever)

NOTE: There is no sorting and filtering by custom fields.