I use Ancestry.com a lot. It is a paid service ($) but well worth the fee – monthly or annual – to get access to so many records worldwide. But I also find FamilySearch.org, a FREE service with lots of records, useful too. There are many other sites with records online but these two sites have the most. Some other resources I use often?

• Cyndi's List is a huge site to help you learn about genealogy research, find where records might be kept, etc.
• Findagrave.com is an extremely useful site for searching cemeteries. It doesn't cotain every grave or even every cemetery but they are working toward it. There are many photos of headstones and a way to to request a photo.
• Rootsweb.com is a free source of information from Ancestry.com.
• USGenWeb.org breaks the country into states and then counties to help you find where records can be found. Some sites include actual records, many of which are just transcriptions.

I'm sure there are others. What are your favorites?