YASnippet had been my go-to package until I came across this thread. Now I'm excited about yet another Emacs template system named "TempEL". YASnippet is undoubtedly a great package for handling snippets formatted like in TextMate. The only drawback I often encounter is that the package manages each snippet in a separate file, and acquiring the snippet format can be slightly challenging. TempEL addressed this concern with the 'tempo' format, which has been around in Emacs for decades.
The following two templates are used to create the same skeleton for a blog post in Org-mode, using YASnippet and TempEL as the respective tools.
YASnippet
# -*- mode: snippet -*-
# name: blog-post
# key: blog
# --
* ${1:blog_title}
SCHEDULED: ${2:`(format-time-string "<%Y-%m-%d %a>")`}
:PROPERTIES:
:EXPORT_FILE_NAME: ${3:`(format-time-string "%Y%m%d_%H%M")`}
:END:
${0:`(org-expiry-insert-created)`}
TempEL
(blog & (org-insert-heading-after-current)
(p "blog title: " title t) (insert title)
(prog1 nil (org-schedule nil (current-time)))
(org-entry-put (point) "EXPORT_FILE_NAME" (format-time-string "%Y%m%d_%H%M")))
As you can see, the TempEL format allows you to write templates in full Lisp data code, whereas YASnippet's format permits the use of Lisp code to a limited extent, as long as the code does not directly manipulate buffer contents. That's the point I'd like to recommend TempEL to Lispers and Emacs enthusiasts. You can see my TempEL templates being incorporated into my configuration collection.