my experience is by the time you fart around trying to find the free topo that you need, you can buy the dirt cheap USGS maps and finish the project. at my billing rates, the free topo is not really free...
it's a little bit of a pain to get all the software up and running but the directions are farely straigtforward. it'll generate topo maps and you can put the in to a garmin too...but it'll delete anything else on the card if you do upload them to your garmin so plan accordingly.
They provide a google earth layer that shows topo quads at multiple scales, allow printing, exporting, etc. And as far as I've used it it has been free.
i guess there should be an additional question: to what scale maps are you interested?
most usgs maps are 20-30' contours. the generated map link i posted will generate maps to any scale. keep in mind that the quality of maps depends on the database used (1-arc, 1/3 arc, or 1/9 arc).basically, 1/3 arc has 10' vertical accuracy and 1/9 arc has 3' accuracy. they are also reportedly updated annually, but i have seen instances where i would argue that it is not. as always, use any map with caution and confirm the map correlates with field conditions.
The seamless usgs server allows you to select your project site and it will cut out the area from whatever data you have selected (doqq, quad, dem, etc.)
seamless.usgs.gov
Of course it's not good to use this data for final design purposes, but it can give you a general idea.
my post uses seamless server data. the hardest part about it all is that the server doesn't always cooperate...and that will always be when it's a last minute thing and you're in a rush. works good for generating a topo map and then stick it in the gps so that you can use it walking in the field.