The Electronic Code of Regulations published by NARA and GPO is a great resource and stays amazingly current (http://ecfr.gpoaccess.gov/). However, the links to items appear to be based dynamically on the node position of the item with the larger Title and Part document. When preceding items are deleted or added, the link to a given item changes.
So, for example, a link to 17 CFR 240.15c2-12, will change when new 17 CFR 240 items are added or deleted prior to this item.
If item links had a permanent url, the resource would be easier and more reliable to use.