Though his later writings get a lot of attention, Rilke's early period is also cherished by many readers. Especially in Germany the poems he wrote between 1899 and 1903 are particularly praised as the work of a master. These poems were published together in the collection Das Stundenbuch, which is divided into three parts, Das Buch vom mönchischen Leben, Das Buch von der Pilgerschaft, and Das Buch von der Armut und vom Tode. These poems are very much concerned with the fin de siecle, with modernity, and with love, loneliness, and God. But yet these terms are misleading. The loneliness is less wallowing than solitude, God is less of a presence than an absence, addressed like a lover, and time is at once composed of eternal hours and fleeting moments.
There are English translations available but as is often the case with poetry, they don't really do the originals much justice. So for those of you who can read German, here follows the very first poem of the collection.

Da neigt sich die Stunde und rührt mich an
mit klarem, metallenem Schlag:
mir zittern die Sinne. Ich fühle: ich kann--
und fasse den plastischen Tag.

Nichts war vollendet, eh ich es erschaut,
ein jedes Werden stand still.
Meine Blicke sind reif, und wie eine Braut
kommt jedem das Ding, das er will.

Nichts ist mir zu klein und ich lieb es trotzdem
und mal es auf Goldgrund und groß,
und halte es hoch, und ich weiß nicht wem
löst es die Seele los...

The second poem is infinitely more famous, with its first line arguably the most well known clause he ever formulated....
Ich lebe mein Leben in wachsenden Ringen