On Linux, blocked processes also contribute to the load averages. The command
ps -Al lists all processes. In the second column (S for State) of its output you will find the process states. Most often I have processes waiting for disk "D", which are counted towards the load averages.
The full list of states from the ps man page is
D Uninterruptible sleep (usually IO)
R Running or runnable (on run queue)
S Interruptible sleep (waiting for an event to complete)
T Stopped, either by a job control signal or because it is being
W paging (not valid since the 2.6.xx kernel)
X dead (should never be seen)
Z Defunct ("zombie") process, terminated but not reaped by its
F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME CMD
4 S 0 1 0 0 80 0 - 4906 poll_s ? 00:00:23 init
1 S 0 2 0 0 80 0 - 0 kthrea ? 00:00:02 kthreadd
1 R 0 3 0 99 80 0 - 0 ? 01:00:02 runner
1 D 0 4 0 1 80 0 - 0 ? 01:00:02 loader
If these were your only processes you we see a load of about 2, 1 for the CPU hog "runner" and another 1 for the loader which is waiting for disk.
Very precise is the information available on Wikipedia
An idle computer has a load number of 0. Each process using or waiting
for CPU (the ready queue or run queue) increments the load number by
1. Most UNIX systems count only processes in the running (on CPU) or runnable (waiting for CPU) states. However, Linux also includes
processes in uninterruptible sleep states (usually waiting for disk
activity), which can lead to markedly different results if many
processes remain blocked in I/O due to a busy or stalled I/O
system.1 This, for example, includes processes blocking due to an
NFS server failure or to slow media (e.g., USB 1.x storage devices).
Such circumstances can result in an elevated load average, which does
not reflect an actual increase in CPU use (but still gives an idea on
how long users have to wait).