I'm focusing a lot of my energy on cloth diapers because they're cute, fast, and I don't know yet what other people are giving/handing down to us! I have also made a couple tiny lap tees.
I'm knitting a blanket -- super quick, just 7 think bands of different colors in garter stitch, so it's squishy and bold-looking (I get so tired of pastels for babies...) and I plan to make a quilt as soon as the right pattern calls to me. I am also eyeing a knitting pattern called the "manly vest" (though I think it looks pretty neutral...) that could be good all year in a lightweight yarn.
In the August DDC it looks like a lot of mamas are knitting baby cocoons for their newbies -- seems like in a light enough yarn that might be fine for summer, depending on where you live! Then again, I live in New Hampshire, where even *I* need a sweater at some point during most months of the year....
Other things I plan to make soon are some upcycled sweater longies/wool covers, a couple of t-shirt baby gowns, and maybe another style of carrier (I have an Ergo already that I found at a thrift store for $10 when I was nannying - love that thing!). When we get a changing pad I will definitely make a cover for it because, again, don't love pastels.
Oh! I made one pretty frivolous thing -- there is a tutorial floating around Pinterest for a stuffed whale made of blue jeans, which I just could not get out of my head. So I sewed that up and am stuffing it with the scraps of all the other things I've been making ^__^
I do like the idea of decorating onesies. Embroidery or stamping or applique could all be fun :) I've also seen neat things done with a bleach pen on black onesies, though I would love to know where to get black onesies easily!