Windows Updates - Visit this website, at least once a week to download the latest security updates and patches for Windows.

Antivirus and Antispyware
Ad-Aware - A great free antispyware utility. Use in conjunction with Spybot
Spybot - Another very useful utility to get rid of spyware on your machine.
Panda ActiveScan - Free online antivirus scan.
Trendmicro Housecall - Another good free online antivirus scan

Dialup Links
Why Don't High Speed Modems Work at Their "Rated" Speed? Very good reading, tons of information
56k.com

Tweaks
Optimizing.net
TechSpot - Tweaking your modem
UpsetChaps Gaming Connection Guide

Modem Drivers
DriverGuide

Support Sites*
Modemsite.com
Awolfpup's Guide to Speed Issues