You should download an archived update site. JBoos Tools 3.2.0.CR1 is placed on
http://download.jboss.org/jbosstools/builds/development/3.2.0.CR1/sf.net/jbosstools-3.2.0.CR1.aggregate-Update-2011-01-23_08-34-59-H190.zip
Check if the download is successful. The size of the downloaded file should be 173,225,467 bytes. Recently there is a problem with the sourceforge site so there is a possibilty you haven't downloaded the complete file.
You don't need to unzip it, but call Help>Install New Software>Add>Local and point to the zip file you downloaded.
If you want to install the JBoss Maven Integration, JBoss BIRT Integration and JBoss TPTP, you also need to install m2eclipse-core 0.12.x, m2eclipse-wtp 0.11.1, BIRT and TPTP runtimes.
M2eclipse can be installed only using the following update sites:
http://m2eclipse.sonatype.org/sites/m2e/
http://m2eclipse.sonatype.org/sites/m2e-extras/
BIRT and TPTP can be downloaded from:
http://www.eclipse.org/birt
http://www.eclipse.org/tptp
If you want to install JBoss Tools to the dropins directory, you can create a script like the following:
<ECLIPSE_HOME>\eclipse.exe -nosplash -consolelog -application org.eclipse.equinox.p2.repository.repo2runnable -source file:///<YOUR_DIRECTORY>jbosstools-3.2.0.CR1.aggregate-Update-2011-01-23_08-34-59-H190.zip C:\jbosstools
on Windows (YOUR_DIRECTORY looks like C:/downloads, not C:\downloads)
or
<ECLIPSE_HOME>/eclipse -nosplash -consolelog -application org.eclipse.equinox.p2.repository.repo2runnable -source file:///<YOUR_DIRECTORY>/jbosstools-3.2.0.CR1.aggregate-Update-2011-01-23_08-34-59-H190.zip ~/jbosstools
on Linux.
JBoss Tools features and plugins will be placed in the jbosstools directory. Copy the features and plugins directory to <ECLIPSE_HOME>/dropins/jbosstools/eclipse and restart Eclipse.