Here's some ideas for Bitcoin businesses. Feel free to use them or share more ideas. If you get rich with one of them, I will be happy to accept your donations.
I wanted to start some of these business but since I won't have the time soon, I prefer that someone else develops them.
1) Ripple Proxy node
To increase Ripple liquidity, your company can act as a router. You accept bitcoin deposits from your clients, and extend them Ripple IOUs for the same amount they deposit. Then anyone can redeem your IOUs to you for the equivalent funds in reserve.
As you redeem your debts almost instantly, many nodes will trust you and you will become a highly connected node. It's useful to have IOUs from a highly connected node and that's why your clients deposit funds.
You rely on withdrawal fees. Your clients want increase their Ripple liquidity.
2) Custom lottery
There are a few bitcoin lotteries, double or nothing bets and the like, but there's no unified place to play them all.
It would work like this: the customer chooses the ticket price and the probability. If there's already a draw like that, he joins it.
If not, a new draw is created. Note that different ticket prices could be combined by the system within the same draw if the probability is the same.
The harder to win, the more you get. The draw creator can set a limit Date/block number. If there's not enough participants in the draw when the block number/date is reached, the system sends back all the money.
Participants don't have to log in. When a draw is created, a new address for the escrow is created by the system and is shown in the column target address of the "all draws" table.
Users can search for draws with different filters. They just send their bitcoins to the indicated address. If the sent payment is not equal to the ticket price, the payment is sent back by the system.
The algorithm should be known and depend on the hash of the next block when all the funds for the draw are there.
3) Payments manager
There's a lot of concern with the instability of the bitcoin price and how many people reject to use it for that reason.
Merchants that don't want to hold bitcoins can hire your services. You help them to set bitcoin prices syncronized with the spot price of bitcoins in exchanges.
When you receive a bitcoin payment, you can either sell them automatically using the various exchanges or hold them and use options to warranty you stay solvent.
The merchants don't have to cash out their sells instantly. They can do it from time to time to save in banks fees.
They can also make bitcoin payments from your web, even if their funds are not denominated in btc.
Bitcoiners can also deposit funds to pay merchants that don't trust bitcoin but trust you, even if they don't want to have btc prices and payments.
You can establish a POS payment system too or participate in the Account Hub project
(is it still alive?).
Critiques are welcomed too.