I have certain old CD/DVD's which are not in good condition. I want to recover from them anything that can be recovered. in windows you had software like Isobuster and Cd Recovery which will let me do this. Can anyone suggest a native linux app?
For Ubuntu, try dvdisaster for data cd's and dvd's. Really good if you like graphical tools. It's tricky to use with commercial movie dvd's, though. You'll have to open the dvd in Totem once first to "authenticate" the drive. After that, it works well.
You also have ddrescue for the terminal.
I have used both, and they are good.
Once you have the file on your hard drive you can try "uncompressing" it, or mounting it. If it's too damaged, I resort to foremost or testdisk to get all possible files out of the dumped image of the disk. Here is a quick link: http://www.ubuntugeek.com/recover-deleted-files-with-foremostscalpel-in-ubuntu.html
Not sure about music cd's, though. Look for a cd-ripper that uses cdparanoia. I haven't needed to do that in a long time. A quick search shows abcde, ripperx, and more.