G.L.
Check out Khan Academy, a free online school. I am currently using the K12 curriculum independently and supplementing our math through Khan Academy, and I really like what I've seen there. One of my friends uses Khan Academy almost exclusively with her sixth grader, and has gotten positive results.
Also look at www.openculture.com for loads of free educational resources. PBS has great online resources. Colonial Williamsburg does, too. and once a year they have special virtual field trips that are free to homeschoolers. Lots of universities host free online educational content for kids in subject areas such as classical mythology, science, and history. These can often be found by googling by subject or topic.
Go looking in your community for live resources, too. Many museums run school programs that homeschoolers can get in on if they ask. Also, local symphonies, ballets, and theaters often hold performances for school kids that homeschoolers can participate in, for reasonable prices or even for free, if they ask. Get on the phone and see what you can find out. Public libraries are also a great place to look for events and special programs.