The Water Sampler
This is issued approximately monthly from the STEP office, and covers many items related to LID, including notices of significant updates to the Planning and Design Guide.
You can sign up on the STEP website.
If you use an RSS or atom feed reader in your web browser, you can subscribe to automatic updates from the planning and design wiki on the page Special:RecentChanges.
The link appears in the left menu labelled 'ATOM'.
If you want to conduct your own check for updates since your last visit; again the page Special:RecentChanges automatically logs all changes.
You can filter results by total number and by number of days history (up to one month).