EasyBid is a good way to view your choices offline and actually move step by step through the bid logic. It saves you a ton of time online, since you enter everything offline and just upload when done. The Navtech Desktop software does the same thing, but I didn't find it as user friendly.
Additionally, EasyBid allows you to import the bid data after the schedules come out and analyze your results. It will show you what trips were available at your seniority level. It's useful for analyzing and improving your bidding strategy.
The software is free, but the data connection costs 9.95 per month for unlimited use. It's helpful if you plan to use the companion software EasySwap to work open time and swap trips. If you just want to bid and nothing else then the per kB plan only charges you for connect time. Expect to pay less than $5 per month if you just send bids and download the bid pack and schedule.
Hope this helps.