Source download
Latest version is 1.2.10; download tarball from here.Installation is as simple as:
gzip -dc aspseek-1.2.10.tar.gz | tar xf - cd aspseek-1.2.10./configure make su make install
Actually, after extracting the tarball, please read at least README and INSTALL files - they contains some useful info.
Other useful things you can do with ASPseek sources are:
Making RPMS
If you are on RPMS-based system like RedHat, you can build your own ASPseek RPMs just by issuing:./configure make rpms
Making a manual
You can build a nice-looking ASPseek manual in PDF format by issuing:make manual