In traditional Wicca there's a poem known as the 'Witches' Rune', which is often chanted as part of the opening part of rituals, possibly accompanied by a dance. It was originally written by Gerald Gardner and Doreen Valiente, and can be found for example in Janet and Stewart Farrar's Eight Sabbats for Witches.
Skimming through books for possible material to use in rituals, I happened again upon this poem that in the past I'd mostly ignored, and found it somewhat appealing. I wouldn't use all of it, as much of it refers specifically to Wiccan ritual tools etc. that aren't really currently relevant to me. But the following two stanzas are relatively neutral and usable for invoking some general Wiccan-flavoured Goddess and God energies. (I've adapted the wording very slightly to appeal to me better, borrowing from several versions of the poem.)
Darksome night and shining moon,
East and south and west and north;
Hearken to the Witches' Rune,
Hear me now, I call ye forth!
Queen of heaven, queen of hell,
Hornèd hunter of the night,
Lend your power to the spell
Work my will by magic rite!
Essentially, these two verses summarise the entire Wiccan circle ritual, as they invite the powers of the four quarters and the Goddess and the God. Optionally the obscure chant 'Eko Eko Azarak, Eko Eko Zomelak!', repeated to your heart's content, may be added to the Rune.
A third segment of the Rune could also perhaps be used, potentially at the end of a magickal working:
By all the power of land and sea,
By all the might of moon and sun,
As I do will, so mote it be,
Chant the spell, and it be done!
The Farrars' book The Witches' Way contains a version of the Gardnerian third degree initiation ritual put into verse by Doreen Valiente. Here are some excerpts from that text that could be used just as well in other ritual contexts (I changed a few of the pronouns to better suit solo working):
Assist me to build,
As the Mighty Ones willed,
The altar of praise,
From beginning of days.
Be this, as of yore,
The shrine I adore,
The feast without fail,
The life-giving Grail.
By rushing wind and leaping fire,
By flowing water and green earth,
Pour me the wine of my desire
From out thy cauldron of rebirth.
The first two excerpts would seem appropriate for use at the beginning of a ritual, before (or during) the act of tracing the circle. The third, on the other hand, is a perfect blessing for a ritual drink. (Originally these verses refer particularly to the body of a woman as an altar, but I see no reason why they couldn't be used to bless any sacred space.)
The Grail reference might feel a little too Christian to some. Another couplet from the poem that could be used instead is: 'Invoked in this sign, the Goddess divine.'
Here's a short snippet from a poem by Aleister Crowley, titled 'The Altar of Artemis':
And like the slumber of the seas,
There murmur through the holy trees
The kisses of the goddess keen,
And sighs and laughters caught between.
The following lines are from the Orphic Hymn to Pan (from the late Hellenistic or early Roman era), translated by Thomas Taylor (this appears to be a slightly shortened version, but I like its flow better):
Come, blessed Pan, whom rural haunts delight,
come, leaping, agile, wand'ring, starry light.
Throned with the Seasons, Bakkhanalian Pan,
goat-footed, horned, from whom the world began.
The following segment of the same hymn references the four elements:
By thee the earth wide-bosomed, deep and long,
stands on a basis permanent and strong.
The unwearied waters of the rolling sea,
profoundly spreading, yield to thy decree.
The spacious air, whose nutrimental fire,
and vivid blasts, the heat of life inspire;
the lighter frame of fire, whose sparkling eye
shines on the summit of the azure sky,
submit alike to thee, whose general sway
all parts of matter, various formed, obey.