diff --git a/README.md b/README.md
index 4ee490a..7ee6264 100644
--- a/README.md
+++ b/README.md
@@ -33,15 +33,17 @@ checkout.
    ("upstream") hub
 
  - Support for polling and push-notification for remote topics, with
-   configurable poll interval
+   configurable poll interval; this allows *hub chaining*.
 
  - Uses HTTP `Link` headers when retrieving a topic to determine
    canonical hub and topic URLs; does not extract `link` elements from
    any kind of XML or HTML document, nor does it implement
    `.host-meta` discovery
 
- - Support for `hub.secret` and `hub.lease_seconds` protocol
-   parameters
+ - [WebSocket](https://tools.ietf.org/html/rfc6455)-based
+   subscriptions to WebSub topics, in addition to the usual
+   [WebHook](https://en.wikipedia.org/wiki/Webhook)-based
+   subscriptions.
 
 ## Configuration
 
@@ -207,6 +209,39 @@ At the time of writing, no official list of conformance criteria
 exists; however, there is a draft list of Candidate Recommendation
 implementation criteria at <https://github.com/w3c/pubsub/issues/56>.
 
+## Codebase Layout
+
+Files at the toplevel of the git checkout:
+
+ - `COPYING`, `gpl.txt`, `lgpl.txt`: Licensing and copyright information
+ - `info.rkt`: Racket package control metadata
+ - `nginx.conf`: Example nginx configuration file, for running RacketMQ behind nginx
+
+In the `racketmq/` directory are the sources for the RacketMQ server:
+
+ - `hub.rkt`: **Main entry point for RacketMQ server**
+ - `config.rkt`: Actor that tracks changes in config files
+ - `protocol.rkt`: Definitions of protocol structures for coordination among RacketMQ actors
+ - `hub/`: Source code for the main functions of the RacketMQ server
+    - `hub/static-content.rkt`: Actor serving static content from `htdocs/`
+    - `hub/subscription.rkt`: Actors implementing downstream WebHook-based subscriptions
+    - `hub/websocket.rkt`: Actors implementing downstream WebSocket-based subscriptions
+    - `hub/topic-demand.rkt`: Actor that analyzes a subscription topic
+      URL, deciding whether it represents a local topic or a remote
+      topic.
+    - `hub/local-topic.rkt`: Actor implementing a local RacketMQ topic
+    - `hub/remote-topic.rkt`: Actors implementing a remote RacketMQ
+      topic and WebSub subscribers that relay content from upstream
+      hubs (if any) to downstream subscribers
+
+The `racketmq/` directory also contains a few other files of interest:
+
+ - `defaults.rktd`: Fully-commented RacketMQ configuration file
+ - `poke.rkt`: Simple interactive tool for interacting with RacketMQ
+ - `run`: [Daemontools](https://cr.yp.to/daemontools.html) startup script for the server
+ - `log/run`: Daemontools logging startup script for the server
+ - `htdocs/`: Static files to be served by the server
+
 ## Bug Reports
 
 Please report issues using this project's Github issues page,
diff --git a/TODO.md b/TODO.md
new file mode 100644
index 0000000..67bbd81
--- /dev/null
+++ b/TODO.md
@@ -0,0 +1,26 @@
+
+✓ HEAD for racketmq topic links
+
+✓ Proper async verification
+
+✓ Split implementation into multiple modules
+
+✓ Remove "unbounded" lease duration
+
+✓ Configurability
+
+✓ Explain codebase layout in README
+
+CORS (ugh ugh ugh)
+
+Secrets
+
+Allow secret of a subscription to be changed
+
+Durable subscriptions and other kinds of hub state
+
+Make second-and-subsequent subscriptions to remote topics behave the same as first subscriptions:
+ - randomize the first poll of the content
+ - never do a poll if the poll interval is "none" for the topic as a whole
+
+Local topic history retention and browsing