Found a few great Ideas for Bitcoin Software Devs.
http://bitcoin-hackathon.com/index.php/Main_PageBitcoin powered video game
Point Of Sale system
P2P local trader system
Marketplace
Electrum style clients
Brainwallet "offline" HTML5 connecting to stratum servers with deterministic keys and no storage at all.
Mobile dev
Art installations
Street project with Bitcoins
Anonymising services
Bitcoin prediction market - Intrade clone (hard)
BitcoinQR service with currency conversion (easy)
ElectrumPOS - easy, safe, painless way of accepting bitcoins at some shop
Anonymous double-blind review portal for scientific papers with moderation and meta-moderation (hard)
Translation Tool with btc bountys for translations - download to popular xml/yaml/properties files. (medium)
Offer your wifi for Bitcoin in a neighbourhood -> incentivises people to create mesh networks
POS system to print QR codes to receive payments in a restaurant.
Board to display payments for orders at a restaurant.
New graphics / icons
UI review of Bitcoin clients, and improvements
Design perfect Bitcoin system
GuessMyBrain - a bitcoin challenge game with the aim of guessing the pass-phrase of a brain wallet according to a riddle with limiting rules, and taking the jackpot simply by spending that wallet.
MyOtherHalf - a bitcoin social game that forces two random people to cooperate in order to spend a brain wallet which is created using the two secrets and the combined amount of bitcoins.
gittip.com competitor - funding open source development
Proof of concept for Off-the-chain transactions for details visit /wiki on Ultra Bitcoin Bank
Site for people to get medical advice by paying doctors.
A simple tool, with you can write and read messages to block chain, using transaction data (amounts), public keys or any methods.