The number of inodes that can be created on a linux system is typically extremely massive. The exact number depends on a LOT of variables, but here's a thread on the Ubuntu forums about calculating inodes for your system and about how to show information through terminal commands.
Edit (Ubuntuforums thread now requires login):
Here's essentially what the thread says, and references Wikipedia.
It varies. First off, depending on what file system your Linux install uses. The default is ext3, but even within that filesystem, the maximum number of files varies. From Wikipedia:
The maximum number of inodes (and hence the maximum number of files
and directories) is set when the file system is created. If V is the
volume size in bytes, then the default number of inodes is given by
V/2^13 (or the number of blocks, whichever is less), and the minimum
by V/2^23. The default was deemed sufficient for most applications.
The Wikipedia quote is cited as plain text, so there's no verifiable source, so that's pretty much the end of that trail.
I think the bottom line is that unless you've filled your disk with billions of tiny files, you're probably going to run out of disk space before you run out of inodes.