I am sentimental and I believe that the best memories a child will have are the ones where there was a labor of love. No amount of money, no expensive gifts and toys can substitute the ones that are hand made. They ones that have the greatest impact are the ones that are the most personal. The ones that show time spent and time shared. Amongst my first projects as a mom-to-be was handcrafting a mobile for my baby's crib.
One of the first learning tools your baby will see is the mobile dangling above their crib. They will spend a great deal of time in their first months on their backs and staring up. Given the significance of this I was not drawn to store-bought mobiles; as they all had such a regular pattern, frequently having the same items making up the entire mobile. I am sure for the moms who must have the perfect color coordinated accessories to go in their baby's room, an abstract handcrafted mobile may not be appealing, but it may be in your baby's best interest.
It may also be of interest to note that initially all babies see in black and white, so it is wise to choose a variety of shapes and patterns to stimulate their minds. Lucky for me my husband is an amateur at wood work and made a simple wooden frame with some metal hooks in the arms that I could easily tie different objects on to.
While you don't have to get this technical it should not be so hard to craft your own frame e.g. with some old wood clothes hangers tied together or you could go ready-made and get a plastic round clothes hanger. Either way the best part is getting creative with the accessories that makes up the mobile. Take lots of pictures for that scrapbook and photo album!
I used lots of items that I had from my baby shower; little alphabet blocks and shower favors did a great job. Even though baby will not be able to see in color at the start, they will eventually so don't hold back! I had strings of beads linking between the arms and some of the items made noises when rocked. There are a lot of oddities that you can use from right around your home that would make great accessories for your mobile. Better yet, if you really have the patience (and talent), handcraft your own.
I still remember how pleased I felt when my first daughter scowled her little eyebrows in intense concentration at her mobile, turning her head to each side and studying its every angle out of the corners of her eyes. I was even more happy when she first pulled herself straight up in her crib and reached up to gradually start knocking it around and dismantling it bit by bit.