*All of my music is still on my ipod, but nothing is showing up in my library when I open itunes*
Do you mean your library on the iPod is missing when you view it in iTunes or that your iTunes library is missing? If it's your iTunes library that is empty try holding down the Shift key in Windows when launching iTunes 7. In the resulting dialogue you will get the option to create a new library or navigate to an existing one. The default location for your iTunes library is in C:\Documents and Settings\Username\My Documents\My Music\iTunes\ (or C:\Username\Music\iTunes\ in Vista). Look in there and see if you have more than one library file (they have the extension .itl) If you have more than one try opening them in turn, you may find your original library is still intact:
How to open an alternate iTunes Library file
*can I manually sync by music to my library?*
If you have any iTunes Music Store purchases the transfer of purchased content from the iPod to authorised computers was introduced with iTunes 7. You'll find details in this article:
Copying iTunes Store purchases from your iPod or iPhone to a computer
The transfer of content from sources such as songs imported from CD is designed by default to be one way from iTunes to iPod. However there are a number of third party utilities that you can use to retrieve music files and playlists from your iPod. I use Senuti but have a look at the web pages and documentation for the others too, you'll find that they have varying degrees of functionality and some will transfer movies, videos, photos and games as well. This is just a small selection of what's available, you can read reviews and comparisons of some of them here:
Wired News - Rescue Your Stranded Tunes
Comparison of iPod managers
Senuti Mac Only
PodView Mac Only
PodWorks Mac Only
iPodDisk PPC Mac Only (experimental version available for Intel Macs)
TuneAid Mac only (iPhone and iPod Touch compatible)
iPodRip Mac & Windows
YamiPod Mac & Windows
Music Rescue Mac & Windows
iGadget Mac & Windows (iPhone and iPod Touch compatible)
Floola Mac & Windows
iRepo Mac & Windows (iPhone and iPod Touch compatible)
iPod Access Mac & Windows (iPhone and iPod Touch compatible)
TouchCopy Mac & Windows (iPhone and iPod Touch compatible - Windows version only)
There's also a manual method of copying songs from your iPod to a Mac or PC. The procedure is a bit involved and won't recover playlists but if you're interested it's available on page 2 at this link:
Copying Content from your iPod to your Computer - The Definitive Guide
