This page demonstrates how you can tame a very long Sharepoint list form by
breaking it into expandable sections.
The form to the left is simply the NewForm for a list called Complicated
List, which has a Title column and 100 other columns named Column_1 -
By applying some jQuery and some simple CSS, we can add sections to the form
to make it a little bit easier to use.
It's worth noting two cool things about the form:
- If you pass a section's short name on the Query String, that section will be
expanded on page load. Try ?section=SectionN, where N=[1-6], or click one of these links: 
- If you try to save the form and there are validation errors, the sections
which contain those errors will be expended.
My blog post introducing this idea is here.
You can see the script which makes this work here.
You can see the CSS which makes this work here.