One sided friendships, they are frustrating-should I keep the friendship going?

I have a few friendships in my life that seem so one sided. It is usually me doing the emailing/communicating with my female friends to get together or to have a playdate with our kids. Although I am thankful for these friendships, a part of me feels that it gets really old after awhile with ME being the main person who tries to keep the friendship and communication going. In a way, I sometimes feel that maybe my friend does not care about me or our friendship? I don't know, maybe I'm reading too much into it but I just feel like a friendship should be a two way street, know what I mean? Do you any of you have friendships that are like this? how do you feel about it or are you just used to it? have you ever thought about having the friendship slowly fizzle out? I guess it might depend on how close you would feel with a certain "friend"?

I have a few that i have known forever but we only see each other a few times a year at our kids birthday parties because we live about an hour away and i have some that we do things occasionally because its just hard to find the time. Either way we have been able to pick up where we left off. But i have some newer friends that its like you say you initiate. It sounds harsh but ive stopped trying so hard. I feel like ive given everything i had and they dont care. So i let them call me and focus on my older friends as they seem to appreciate it more. If they call then if you are free id say go. Other than that i dont think they deserve the time of day to fret over.