I've no idea how tech savy users on this forum are, but additionaly I would suggest that disabling the following will give that extra bit of bandwidth for Firefox 3.5+
In "Options" Disable...
Automatic check for updates - Firefox/Installed Add-ons/Search Engines
Block reported attack sites
Block reported web forgeries
JavaScipt (only use it where necassary)
Don't include any RSS feeds!
Also here's some handy addons for dialup users using Firefox:
Download Helper - Useful for downloading videos on Youtube.
Download Statusbar - A statusbar with speed, percentage, time and loaded size.
Extended Statusbar - Puts downloads into the statusbar.
Flashblock - Enable/Disable Flash (JavaScript enabled) with simple on/off icon.
Flash Killer - Stop Flash manually with icon (JavaScript Disabled).
Gmail Notifier (if using Gmail) - saves time logging in through Gmail.com (remember to use the 'Low-Bandwidth' option in Gmail while loading, it's a whole lot quicker!).
Google Enhancer - Some handy alterations to Google search/images - including 'search by date' on main page.
Image-Show-Hide - (Essential) Allows the user to switch off images with an on/off icon.
Menu Editor - Useful for changing Firefox's default right-click menu.
Quick Java - Allows you to switch off JavaScipt and Java with on/off icons in statusbar.
Save Complete - Saves web pages completely with all content intact.
Show Picture - (Essential) Allows you to view individual images when a page has been loaded without images switched on using the right-click menu.
If anyone else has any tips for speeding up Firefox or and cool addons that are helpful to Dialup/low-bandwidth users please share! :o)