I am doing a day by day reading of the Dhammapada right now on
another forum: http://forums.about.com/n/pfx/forum.aspx?
msg=1251.3&nav=messages&webtag=ab-buddhism

And I'm puzzled by the reference's regarding vs 30: By Heedfulness
did Indra become the overlord of the gods.

Sources elsewhere report that the story of Indra/Sakka/Magha is in
the Maghamanavaka Jataka, but I can find no such Jataka. All google
searches for Maghamanavaka take me back to footnotes to the
Dhammapada. I do come across the following, but I don't know what
it's source is:

II (7) The Story of Magha

While residing at the Kutagara monastery near Vesali, the Buddha
uttered Verse (30) of this book, with reference to Sakka, king of
the devas.

On one occasion, a Licchavi prince, named Mahali, came to listen to
a religious discourse given by the Buddha. The discourse given was
Sakkapanha Suttanta. The Buddha spoke of Sakka vividly in glowing
terms; so, Mahali thought that the Buddha must have personally met
Sakka. To make sure, he asked the Buddha, and the Buddha
replied, "Mahali, I do know Sakka; I also know what has made him a
Sakka." He then told Mahali that Sakka, king of the devas, was in a
previous existence a young man by the name of Magha, in the village
of Macala. The youth Magha and his thirty-two companions went about
building roads and rest houses. Magha took upon himself also to
observe seven obligations. These seven obligations are that
throughout his life, (1) he would support his parents; (2) he would
respect the elders ; (3) he would be gentle of speech; (4) he would
avoid back-biting; (5) he would not be avaricious, but would be
generous; (6) he would speak the truth; and (7) he would restrain
himself from losing his temper.

It was because of his good deeds and right conduct in that existence
that Magha was reborn as Sakka, king of the devas.

Then the Buddha spoke in verse as follows:

Verse 30. Through mindfulness (in doing meritorious deeds) Magha
became king of the devas. Mindfulness is always praised, but
negligence is always blamed.

At the end of the discourse Mahali attained Sotapatti Fruition.

-DaveK