You definitely don't need to have $3000 minimum to buy stocks, and you DEFINITELY don't want to "share the shares" with your friend. It could create tax problems and friendship problems.
Plenty of online brokerages let you buy for $4-10 per transaction in any amount. If you and your friend both want to buy the same stock at the same time for some (dumb) reason, you can each just buy whatever amount you want in your own account. A Vanguard brokerage, if it really has this minimum, isn't necessary. I have money with Vanguard for their funds, and buy stock through Schwab and Sharebuilder.
It sounds like you're new to purchasing stocks, so while keeping most of your money in Vanguard index funds, you might want to try out sharebuilder.com, which lets you automatically invest in stocks every month, with small fees. Whatever company it is you're looking at, you could set up so you buy $50 or $100 every single month. You could then follow the stocks ups and downs, see what your risk tolerance is, etc.
But seriously, buying with a friend is just silly. You should each buy your own in your own accounts.