Although there is (not yet) support for building projects in Eclipse with the Haskell Cabal, there is an editor that supports Cabal's package description files.
That editor provides syntax coloring, code folding, a page for the Outline View, and makes also some templates available that let you easily create a new Cabal package description.
The editor is by default registered for the file extension
.cabal. To trigger a template, hit Control+SPACE
at any (non-comment) position in such a file. For some entries (e.g. the
license-file entry, you can also hold the Control
key and point with the mouse on the value - the entry is then changed into
a link that takes you directly to the referenced file (if it exists) when
you click on it.