You can use the http.debian.net redirector to install Debian Wheezy or upgrade to it from Squeeze and make use of Debian's ever-growing 370-large mirrors network to get it.
APT one liner (to be used in your /etc/apt/sources.list file):
deb http://http.debian.net/debian wheezy main
During the installation process you can also choose to use it by manually entering http.debian.net as an HTTP mirror and /debian/ as the path.
Get it while it's hot!