Hoo boy. Have you seen charts?
A lead sheet would be a good way to document your compositions if they are simple pop tunes. This typically consists of staff paper with the melody on the staff, chord changes above the staff, and lyrics below. If you expect specific rhythms for the instruments, you could expand this into a score, where each instrument is on its own line. You use chord symbols, slash notation, or written-out notation as needed depending on the extent to which you want the players to play specific rhythms and notes.
This eBay listing appears to show a fairly detailed score of a pop tune:
EARTH,WIND & FIRE BEST JAPAN BAND SCORE TAB | eBay
Musicnotes.com has sample pages for many of their charts. You might be able to find something that looks like what you need for the genre that you are working in.
It's a great idea to have charts -- they are like an insurance policy against mishaps such as your bassist evaporating just before a high profile gig. Every town has a small cadre of players who enjoy the challenge of taking care of bands that run into these situations. I've played more than my share of "one rehearsal, one gig" engagements.
Even for players who are not singing or playing melody, having those things on the chart is very helpful if we get lost.
