An accountant could certainly help mitigate the taxes here, and it would be worth talking to a reasonably good one about this. There are a few strategies to explore, less since you've already been paid.
As a quick sidenote, if you file taxes on an accrual basis, and you have some sort of warranty period for the software, you can accrue out the revenue equally over the warranty period, so 12 month warranty on software would equal $5k / month in taxable income, much of which would be next year, that would be nice. These sorts of moves are exactly why you'd talk to an accountant in the first place.
The most tax efficient (well, the simplest tax efficient) way to do this in the future would be to sell stock in a corporation that owned the assets. If the company is over a year old, you can get long term capital gains tax rates (15% federal in the US) on sale of stock. That can add up to nice savings quickly.
I don't know if you could keep a few of the companies around and dormant then assign IP and sell stock quickly if you wanted to, but if so, and you're going to make a habit of doing this, that might be a worthwhile strategy. Or, it might be too much headache for a small savings, you'll have to sort it out for yourself with some good advice from a CPA.
Definitely lock some of it away to invest for the long term. Depending on where you are in your life, that could mean anything from buying a (really) cheap rental unit to dollar cost averaging into the NASDAQ to reading Graham and Dodd and working to become a value investor, to.. well you get the idea.
As a practical business matter, I would suggest you try and sell that company a $1-3k a month service contract, probably hour limited with say a 24 month period, autorenewing unless canceled four months in advance. That would offset their risk nicely and would give you some nice stability, offsetting your own.
Finally, I agree with the 'do something fun' advice; I always liked travel myself.
Congrats!