Friendly way of saying "I love you"

If you drop the 'I' it becomes less one-on-one - 'Love You' suggests a generic love for a person - like a rock band or an actress - 'We love you Paul' isn't a personal love, or the hippy 'free love' of the 1960's - 'Luvin' You Man', would go from Brother to Brother, regardless of skin color or religion beliefs. One may love the Lord in a passive way, and the Lord may love you back, but this has no method for determining the nature of the love, probably spiritual. Jesus Loves You, and I hope he will leave it at that.

I often tell friends both male and female that I love them; I don't think it's necessary to diminish the sentiment with flippant phrasing just because it's not romantic love. We don't do this for our family members, and they don't assume we mean we love them in a romantic way. I say trust in the existing context of your relationship; it isn't necessary to quantify or confine it in a single statement.

If you're concerned about the message being misconstrued though, you could add a qualifier, for example: "I love you like a sister" or "I love you like a brother". That would make the nature of the affection clear.

If you qualify the meaning further, you can use the "I love you" such as "You are decent person. I love you, bro". Also, if you are addressing to a group of friends you can say "I love you guys"

The meaning is as much about context and delivery as it is about wording. A sing-songy "Love ya!" as you're saying goodbye for the day can't be taken romantically. On the other hand, being physically close, locking eyes, and saying "I love you." with gravitas is difficult to take any way other than as a romantic gesture. John Mark Perry's answer, suggesting to drop the leading "I" to reduce personal connection, helps a lot to reduce the intensity of the phrase. It's not necessary, however: my friends and I say "I love you" to each other quite often, but in contexts and tones that are always appropriate to the nature of our relationships.