certainly many different solutions that are all fully SE friendly - best is NO javascript - but plain HTML links either in tables on each page example http://www.a1-outdoors.com/ on the right side you see "Site Menu" for smaller sites with few links that is a fully valid solution or my preferred method in SEO friendly frames example http://www.kriyayoga.com/english/on_your_wings/frames_index.html then see left or top frame i have a fedw thousand files to link - hence prefer a method that can be extended as the site grows or subdirectories are created see also old thread about frames http://forums.digitalpoint.com/showthread.php?t=24944 both methods work perfect for ALL major search engines my SE friendly frames-strcutrure works perfect since more than 5 years there are however wrong ways to make frames - for example when frameset file is named index.html
milonic.com has a good drop down menu, its used at the site in my sig. Make it search engine friendly by adding a text only menu in <noscript> tags.
Here's another great resource to help you make a SE friendly dropdown Nav http://www.alistapart.com/articles/horizdropdowns
However, I strongly suggest against drop-down menus unless you can view the links in the HTML Source Code, which search engines will always look at. If you can't view links in the source code your dropdown menu, then I strongly urge that you don't use it.