You have 3 options:
1. Press ⌃⌥⇧H to switch to HTML (or use the status bar)
2. Use New From Template → HTML → … optionally giving
your favorite template a key equivalent via the
bundle editor to make that action easier.
3. Switch the default type for new documents to HTML:
<http://lists.macromates.com/pipermail/textmate/2006-February/008276.html>
Many thanks