Bzip2's home page is at The UK home site. The United States mirror site is here. You can also find it on Red Hat's ftp site here.
See the home sites. Red Hat's intel binary is here. Debian's is here, and Slackware's is here. You can also get these in the analogous places at the various mirror sites.
They come from the Official sites (see Getting Bzip2 for where, or Red Hat has it here).
If you have gcc 2.7.2.3, change the line that reads
CFLAGS = -O3 -fomit-frame-pointer -funroll-loops
to
CFLAGS = -fomit-frame-pointer -funroll-loops
that is, take out the -O3 part. After that, just make it
and install it per the README.