At home, my bike is kept in an unlocked communal bike shed overnight. Consequently, I have a big motorbike chain lock I keep there to secure it, specifically one of these:
http://www.pjbsecurity.co.uk/viewproduct.asp?ProductCode=pjb722
The bike shed has a low-down rack a bit like this:
only rotated 90 degrees to be higher but extending forward less. I back the Silvio into it and secure it with the boxer chain through the underseat gap (thus securing the frame and back wheel). The front wheel/triangle are currently unsecured and I am thinking about a better solution for this.
At work, I keep one of these:
http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_231103_langId_-1_CarSelectorCatalogId__CarSelectorGroupId__varient__categoryId_31389_crumb_33980-31270-31433-62454-62460_parentcategoryrn_31389
The bike racks here are a bit like this:
and I secure the frame using the D-lock through the underseat gap and round one of the poles, with an extender cable through both wheels and attaching to the D-lock.
Since I generally just travel to and from work on the Silvio, I don't carry a lock with me for the commute, but if I want to go somewhere during the day, I carry the mini lock from work with me (it's a whole lot lighter than the motorbike chain).
Cheers,
Rob