"Sun PDF Import Extension
As you can infer, using this extension you could actually import
and modify PDF documents. Text attributes like font family, font
size, weight (bold, not bold), style (italic, not italic) are
imported together with their respective text. With the help of this
extension you could retain font appearance, when a PDF file uses a
font not installed on your system. It can even help you in
importing password-protected PDF files
"English Dictionary(Based on Oxford English Dictionary)
This is one among the most sought after extensions for OpenOffice.
It is basically a port of old format of OED United Kingdom english
dictionary to extension format.
Professional Template Pack II - English
If you are an OpenOffice user and you are disappointed about the
unavailability of good quality templates for documents and
presentations, this is the extension you are looking for. This
template pack consists of about 120 professional quality templates
for OpenOffice.org Writer, Calc and Impress."