Laguna is among the elite ranks of Final Fantasy characters who have more than one canon love interest. The main theme of Final Fantasy VIII is love, so it's to be expected in a way, but several playable characters even in this game don't have a love interest at all, so it's something.
Julia Heartilly was probably Laguna's first love. She is the pianist at the club at the Galbadia Hotel. Laguna loved to go watch her play, he had a favorite table where he always watched, and Kiros and Ward were happy to accomidate him. (Hey, booze!) Laguna is painfully shy around her, however, and can never work up the courage to talk to her, though everyone knows he has a crush on her. Laguna gets painful leg cramps when he's nervous, and always has to sit down.
One night, Julia approached Laguna and asked him to her hotel room. It turns out she'd developed feelings for him, the way he would look at her as if nothing else in the world mattered. They talk, and Laguna tells her about his dream of being a journalist. Julia then shares her ambition- she wants to be a singer, to write her own songs, but she had never had anything to write about until that night. She composes the theme of Final Fantasy VIII, Eyes on Me, about Laguna. Unfortunately, Laguna is called away on a mission the next day, further hijinx ensue, and they never see each other again. Julia waits, but evenutally finds love with a soldier named Caraway, and they marry and have a child named Rinoa. She dies in a car accident some years later.
The song Eyes on Me was both a hit in and outside of the game. It's widely associated with the relationship between Squall and Rinoa, who inherit it from their father and mother respectively. That their parents' love was unfufilled adds a further element of destiny to Squall and Rinoa's relationship.
After the Centra incident, Laguna is found badly injured and he is nursed back to health by Raine, Winhill's barkeep. She has an adopted daughter named Ellone, who immediately develops a liking for Laguna, who in some respects is really just a big kid anyway. Laguna spends time recovering in Winhill and later takes a job as a monster hunter, keeping the forest safe for one and all! Ellone feels that "Uncle Laguna" and Raine should get married, but they just take it as a joke.
Their love develops slowly as they get to know one another. Raine is hesitant, at first, because she knows Laguna will be leaving Winhill shortly, but he just stays and stays. Kiros returns, and when Laguna does not want to join him, remarks on how Laguna has changed. Because Laguna is in love with Raine. He proposes one night, and tears flow down her face, they hug, she says yes, and all is beautiful. It seems there's a happily ever after for Laguna after all.
Of course, this is not what happens. Ellone is kidnapped, and Laguna travels the world in hopes of finding her, leaving his bride behind. She has a child and passes away some time afterward, while Laguna is trying to save the people of Esthar. When Laguna sends Ellone to bring his family back to Esthar, there is no one to find- she is sent to an orphanage. When Laguna is reunited with Ellone, he probably learns what has happened. We see at the end of the game that his thoughts are still with her, though he has learned to move on. When the past and future are broght together, Laguna relives the night they were engaged.
Selphie has a crush on "Sir Laguna," from the party's recollection of his past and the Timber Maniacs magazine articles. She even has a website devoted to him! (Much like...er...me...) Not that anything ever comes of it, or that Laguna reciprocates in any way, but I think it's cute.