"I've been searching for prayers/rituals to Eirene, but I haven't been able to find much, besides new-age/wicca stuff which is not what I'm interested in. If you have anything on Eirene, would you post something about her on your blog?"
The ancient Hellenes were aware of only three seasons: Spring, Summer and Winter, and only these had deities presiding over them--the Hôrai: Eunomia (Good Order, Good Pasture), Eirene (Peace, Spring), and Dike (Justice). They were originally the personifications of nature in its different seasonal aspects, but in later times they were regarded as Goddesses of order in general and natural justice, because these were required for farming prosperity. The association of agriculture with law and order can also be found in the divinities of Zeus and Demeter, for example. She had three more sisters: the Moirai, the Goddesses of fate. Their names are Kloto (Κλωθώ, spinner), Atropos (Ἄτροπος, unturnable), and Lakhesis (Λάχεσις, Alotter).
Eirênê and Her sisters are old Goddesses, being born of Themis and Zeus. Themis is the Titan goddess of divine law and order--the traditional rules of conduct first established by the Gods. She was an early bride of Zeus and his first counsellor and was often represented seated beside His throne advising Him on the precepts of divine law and the rules of fate. Zeus hardly requires an introduction, does he? According to Hesiod in his 'Theogony':
"Next he married bright Themis who bare the Horae (Hours), and Eunomia (Order), Dike (Justice), and blooming Eirene (Peace), who mind the works of mortal men, and the Moerae (Fates) to whom wise Zeus gave the greatest honour, Clotho, and Lachesis, and Atropos who give mortal men evil and good to have." [ll. 901-906]
The Horai, Eirênê, Eunomia, and Dikē
Eirênê was born to Zeus and Themis in a coupling before He took Hera as his wife and queen. Her family tree would look as follows:
Chaos ------------ Gaea
Ouranos --- |
Themis -- Kronos --- Rhea
| --- |
Eirênê was particularly well regarded by the citizens of Athens. After a naval victory over Sparta in 375 BC, the Athenians established a cult, erecting altars to her. They held an annual state sacrifice to her after 371 BC to commemorate the Common Peace of that year and set up a votive statue in her honour in the Agora of Athens.
As for prayers to her; there are actually hymns to her, and a few beautiful prayers that have survived to now. The Orphic Hymn to her is well known and prescribes fumigation from Aromatics.
"Daughters of Jove [Zeus] and Themis, seasons bright, Justice [Dike], and blessed Peace [Eirene], and lawful Right [Eunomia], Vernal and grassy, vivid, holy pow'rs, whose balmy breath exhales in lovely flow'rs. All-colour'd seasons, rich increase your care, circling, for ever flourishing and fair: Invested with a veil of shining dew, a flow'ry veil delightful to the view: Attending Proserpine [Persephone], when back from night, the Fates [Moirai] and Graces [Kharites] lead her up to light; When in a band-harmonious they advance, and joyful round her, form the solemn dance: With Ceres [Meter] triumphing, and Jove [Zeus] divine; propitious come, and on our incense shine; Give earth a blameless store of fruits to bear, and make a novel mystic's life your care."
Another one of my favourites is from Euripides, from his play 'The Suppliant Women' (or 'The Suppliants'):
"How far peace outweighs war in benefits to man; Eirene, the chief friend and cherisher of the Mousai; Eirene, the enemy of revenge, lover of families and children, patroness of wealth. Yet these blessings we viciously neglect, embrace wars; man with man, city with city fights, the strong enslaves the weak." 
In Hómēros' Epigrams we find another line which always moves me:
"Open of yourselves, you doors, for mightly Ploutos (Plutus, Wealth) will enter in, and with Ploutos comes jolly Euphrosyne (Mirth) and gentle Eirene (Irene, Peace). May all the corn-bins be full and the mass of dough always overflow the kneading-trough." [XV]
The link between Eirênê and Ploutos (Πλουτος, 'Wealth') was well-established, and the image to the side depicts both. Ploutos is a son of Demeter, the Goddess of agriculture, who bore him after lying with the hero Iasion in a thrice-ploughed field. He was blinded by Zeus so he would distribute wealth indiscriminately and without favour towards the good or the virtuous. He was almost always depicted as a boy or baby, and was often carried by either Eirênê or Tykhe, the Goddess of fortune. Ploutos was identified with Plouton, the God Haides (Hades) in His role as the deity of the earth's hidden stores of wealth.
In art, She was depicted as a beautiful young woman carrying a cornucopia, the staff of Hermes and a torch or rhyton--a container from which fluids were intended to be drunk or to be poured in some ceremony such as libation.
I hope this is enough to satisfy your curiosity about Her, dear reader, and give you a good start to Her worship.