diff --git a/planet-scheme.scm b/planet-scheme.scm
index 6ac7b1f..d6eea6d 100644
--- a/planet-scheme.scm
+++ b/planet-scheme.scm
@@ -55,22 +55,30 @@
 
 ;;
 
-(define (refresh-cache)
+(define (refresh-cache all?)
   (for-each (lambda (feed)
-              (disp "Refreshing " (feed-url feed))
-              (planet-refresh-feed feed cache-directory))
+              (let ((new? (not (feed-cached? feed cache-directory))))
+                (when (or all? new?)
+                  (disp "Refreshing " (feed-url feed))
+                  (planet-refresh-feed feed cache-directory))))
             feeds))
 
 (define (generate-from-cache)
-  (disp "Writing index.html")
-  (write-html-file "index.html" (front-page)))
+  (disp "Writing www/index.html")
+  (write-html-file "www/index.html" (front-page)))
+
+(define (only-command-line-arg? arg)
+  (and (= 1 (length (command-args)))
+       (string=? arg (first (command-args)))))
 
 (define (main)
   (cond ((null? (command-args))
-         (refresh-cache)
+         (refresh-cache #t)
          (generate-from-cache))
-        ((and (= 1 (length (command-args)))
-              (string=? "-n" (first (command-args))))
+        ((only-command-line-arg? "-n")
+         (refresh-cache #f)
+         (generate-from-cache))
+        ((only-command-line-arg? "-o")
          (generate-from-cache))
         (else
          (error "Usage: ./planet-scheme [-n]"))))
diff --git a/planet.sld b/planet.sld
index 359976b..b565888 100644
--- a/planet.sld
+++ b/planet.sld
@@ -3,6 +3,8 @@
           feed-id
           feed-title
           feed-url
+          feed-cache-file
+          feed-cached?
           entry-author
           entry-title
           entry-content-xhtml
@@ -109,6 +111,9 @@
     (define (feed-cache-file feed cache-directory)
       (path-append cache-directory (string-append (feed-id feed) ".xml")))
 
+    (define (feed-cached? feed cache-directory)
+      (file-exists? (feed-cache-file feed cache-directory)))
+
     (define (planet-refresh-feed feed cache-directory)
       (let ((cache-file (feed-cache-file feed cache-directory)))
         (create-directory cache-directory)