Logo Pond http://logopond.com is a good starting place to get inspirational from what others have done.
Logo Faves http://logofaves.com has some good logos to look at and you can get designers to compete to design your logo!
Logo Fresh http://logofresh.co.uk lets you design your own logo and you only pay if you decide to use it.
Some of the best logos have come from clever use of fonts. Google Fonts www.google.com/webfonts has hundreds of free, open-sourced fonts that you can use.
Font Squirrel www.fontsquirrel.com also has some good fonts.
