I've done this in the FFIX & FFVIII Forums so I shall do one here too.
FFX Couples...

1. Yuna and Tidus
2. Lulu and Wakka
3. Rikku and (If I were in the FFX-2 Forum) Gippal
4. Jecht and Tidus' mom (Did they mention her name anywhere in the game?)
5. Dona and B- forget his name...um...ah ha Barthello?
6. Seymour and well who knows sort-of Yuna
7. Lucil and Luzzu (That'd be cute if he wasn't dead)
8. Previously Lulu and Chappu

That's all I can think of ATM.