diff --git a/README.md b/README.md
index f1b989b..f992650 100644
--- a/README.md
+++ b/README.md
@@ -62,17 +62,17 @@ In addition to the limitations listed below, this software isn't robust. Jekyll,
 ### Current Limitations
 
 Missing features:
+
 - Themes
 - Excerpts
 - Pagination
 - Math
 - CSV and JSON data files
 - Plugins. (Some plugins are emulated. See the [plugin board](https://github.com/osteele/gojekyll/projects/2) for their status.)
-- `site-static_files`, `site.html_files`, and `site.tags`
-- These Liquid filters: `group_by_exp`, `cgi_escape`, `uri_escape`, `scssify`, and `smartify`
+- Template filters `group_by_exp`, `cgi_escape`, `uri_escape`, and `scssify`
 - More Liquid tags and filters, listed [here](https://github.com/osteele/liquid#differences-from-liquid).
-- Windows compatibility
 - Markdown features: [attribute lists](https://kramdown.gettalong.org/syntax.html#attribute-list-definitions), [automatic ids](https://kramdown.gettalong.org/converter/html.html#auto-ids), [`markdown=1`](https://kramdown.gettalong.org/syntax.html#html-blocks).
+- Windows compatibility
 
 Also see the [detailed status](#feature-status) below.
 
diff --git a/site/drop.go b/site/drop.go
index 962e253..d0b5734 100644
--- a/site/drop.go
+++ b/site/drop.go
@@ -10,8 +10,8 @@ import (
 
 // ToLiquid returns the site variable for template evaluation.
 func (s *Site) ToLiquid() interface{} {
-	// double-checked lock is okay here, since it's okay if this gets
-	// written twice
+	// double-checked lock is okay here, since it's okay if this is
+	// computed and set twice
 	if len(s.drop) == 0 {
 		s.Lock()
 		defer s.Unlock()
@@ -32,12 +32,12 @@ func (s *Site) initializeDrop() {
 	vars := templates.MergeVariableMaps(s.config.Variables, map[string]interface{}{
 		"data":         s.data,
 		"documents":    s.docs,
+		"html_files":   s.htmlFiles(),
 		"html_pages":   s.htmlPages(),
 		"pages":        s.Pages(),
-		"static_files": s.StaticFiles(),
+		"static_files": s.staticFiles(),
 		// TODO read time from _config, if it's available
 		"time": time.Now(),
-		// TODO static_files, html_files, tags.TAG
 	})
 	collections := []interface{}{}
 	for _, c := range s.Collections {
@@ -59,6 +59,20 @@ func (s *Site) setPageContent() error {
 	return nil
 }
 
+// The following functions are only used in the drop, therefore they're
+// non-public and they're listed here.
+//
+// Since the drop is cached, there's no effort to cache these too.
+
+func (s *Site) htmlFiles() (out []*pages.StaticFile) {
+	for _, p := range s.staticFiles() {
+		if p.OutputExt() == ".html" {
+			out = append(out, p)
+		}
+	}
+	return
+}
+
 func (s *Site) htmlPages() (out []pages.Page) {
 	for _, p := range s.Pages() {
 		if p.OutputExt() == ".html" {
@@ -67,3 +81,12 @@ func (s *Site) htmlPages() (out []pages.Page) {
 	}
 	return
 }
+
+func (s *Site) staticFiles() (out []*pages.StaticFile) {
+	for _, d := range s.docs {
+		if sd, ok := d.(*pages.StaticFile); ok {
+			out = append(out, sd)
+		}
+	}
+	return
+}
diff --git a/site/posts.go b/site/posts.go
index caf1682..9ed6722 100644
--- a/site/posts.go
+++ b/site/posts.go
@@ -20,15 +20,20 @@ func (s *Site) setPostVariables() {
 		return
 	}
 	var (
-		ps         = c.Pages()
-		related    = ps
-		categories = map[string][]pages.Page{}
-		tags       = map[string][]pages.Page{}
+		ps      = c.Pages()
+		related = ps
 	)
 	if len(related) > 10 {
 		related = related[:10]
 	}
-	for _, p := range ps {
+	s.drop["categories"] = s.groupPagesBy(func(p pages.Page) []string { return p.Categories() })
+	s.drop["tags"] = s.groupPagesBy(func(p pages.Page) []string { return p.Tags() })
+	s.drop["related_posts"] = related
+}
+
+func (s *Site) groupPagesBy(getter func(pages.Page) []string) map[string][]pages.Page {
+	categories := map[string][]pages.Page{}
+	for _, p := range s.Pages() {
 		for _, k := range p.Categories() {
 			ps, found := categories[k]
 			if !found {
@@ -37,7 +42,5 @@ func (s *Site) setPostVariables() {
 			categories[k] = append(ps, p)
 		}
 	}
-	s.drop["categories"] = categories
-	s.drop["tags"] = tags
-	s.drop["related_posts"] = related
+	return categories
 }
diff --git a/site/site.go b/site/site.go
index e9b9510..d36bd8a 100644
--- a/site/site.go
+++ b/site/site.go
@@ -50,16 +50,6 @@ func (s *Site) OutputPages() []pages.Document {
 	return out
 }
 
-// StaticFiles returns a list of static files.
-func (s *Site) StaticFiles() (out []*pages.StaticFile) {
-	for _, d := range s.docs {
-		if sd, ok := d.(*pages.StaticFile); ok {
-			out = append(out, sd)
-		}
-	}
-	return
-}
-
 // Pages returns all the pages, output or not.
 func (s *Site) Pages() (out []pages.Page) {
 	for _, d := range s.docs {