Here are some phrases commonly seen on IRC. Some are not so common, but serve as examples. It is good practice to start every sentence with the word .i, but for the sake of concision, list omits it.

coi Hi
coi ro do Hi, everyone
co'o Goodbye
co'o ro do Goodbye, everyone
do mo What's up? / What're you doing?
go'i Yes (what you just said is true)
na go'i No (what you just said is false)
je'e Roger that. / Okay. / You're welcome.
fi'i Make yourself at home
mi jimpe I understand
mi na jimpe I don't understand
mi'e .maik. My name is Mike
ju'i .maik. Hey Mike! (Listen up!)
doi .maik. Mike, ... (addresses Mike)
re'i Yes? (Expecting speech, typically said after someone says ju'i)
ki'a What?! (I didn't understand one or more words you said)
ki'e Thanks
.u'u Sorry
.u'u sai Very sorry
.u'u cai do cevni fi mi Really very sorry
.e'u I suggest… / Why don't you/we…
.e'o Please
xamgu Good
po'u Which is…
ko gletu lo kanba I am now a true Lojbanist (rite of passage)
.ie I agree
.ie nai I disagree
.i'e I approve
.i'e nai I disapprove
.ui :-) (happy)
.ui nai :-( (sad)
.u'i :-D (LOL)
.u'i nai :-(!! Not funny.
zo'o :-P (only joking)
zo'o nai :-[ (serious!)
.ua Oh! I see! (understanding)
.ua nai Uh… (I'm confused about the meaning of what you said)
.ia nai zo'o No way! (Humourous disbelief)
.a'u That's interesting..
de'a jundi BRB
mi na jundi AFK
lo mi zdani cu se fagri I love IRC so much that nothing else matters
mi co'a jundi / di'a jundi I'm back
mi prami do I love you
mi nelci do I like you
mi na'e birti I'm not sure
mi na djuno I don't know
.au pei mi'o pedysi'u Do you want us to be friends?
lo pluka ko li'i sipna/senva/citka Have a nice rest/dream(s)/meal!
.au cilre fi lo jbobau I want to learn about Lojban/to speak Lojban
.e'o ko ctuca mi fo lo jbobau Please teach me about Lojban/to speak Lojban
.au pei mi'o casnu Do you want to talk with me?
.ei mi sipna I have to go to bed
.ei mi cliva I have to leave
ko ko kurji / ko kurji ko Take care of yourself!
e'o ko e'i denpa Wait a sec..