In the USA
SiriusXM provides a free trial of its online service, with no hardware required. Sign up for free, then use Pulsar to enjoy satellite radio done right.
When the trial is up, SiriusXM Internet Radio costs $12.95 per month.
In Canada
In Canada, Sirius and XM each offer distinct online services, separate from one another and the US service. They also offer free trials.
When the trial is up, XM Canada Online costs $7.99 per month, while Sirius Canada Online costs $14.99 per month.
Airfoil
Wireless audio around your house
Audio Hijack Pro
Record any audio
Fission
Simple & lossless audio editing
Nicecast
Create your own internet radio station
Piezo
Charmingly simple audio recording
Pulsar
Desktop SiriusXM streaming