Yes, you can make daily, weekly, monthly, quarterly or annual donations, as well as one-off donations. (Some of these frequency options might be disabled by individual organisations.)
For donations through Crowdraisers, you can only make one-off donations.
To make a Regular Donation to a cause, click the Regular Donation button before choosing the amount you wish to donate.
On the next screen you can choose the Donation Frequency and set an end date if desired.