SharePoint the Content Editor WebPart (Dark Horse)

Content Editor WebPart or CEWP provides us lot's of capability:

* Write HTML inside it

* Use javascript to do anything
   like
   - calling Sharepoint WebServices
   - create left treeview navigation

* Insert CSS inside the content page

* URL manipulation (i.e. URL Query String or Parameters)

* CSS for Infopath forms (like making tool tip size small) otherwise seems impossible
  
Snippet
"... Using a content editor web part you can insert the required Html (also CSS) into a page. Leveraging this technique we were able to add a content editor web part (CEWP) to our custom application page which hosts the infopath form. This content editor web part envelopes the CSS changes required to the tool tip...."

Now you are free to do anything using CEWP, CSS, HTML, Javascript, Javascript calling SharePoint WebServices and so on.