Not sure how many of us are last-minute filers, but posting here just in case I'm not the only one...
I tried a number of different Free-File websites using the link that theOAP posted. Of the ones the IRS quiz recommended, I tried about 5 before I gave up and paid $7.95 to just be done with it (figured it's cheaper than recorded delivery postage in the end).
FreeTaxUSA: Doesn't support Form 2555 (Foreign Earned Income Exclusion)
1040.com: Something seems to be wrong with their system re: Form 8965. Despite selecting that I lived abroad for the full 12 months, when generating the tax return, it wouldn't put the right exemption code. I also entered all 9's for the NRA spouse's SSN, but the elsewhere I had to select that he was a NRA. But then the system pointed out to me that he shouldn't have a SSN. I tried to go back and delete it, but it was impossible to move forward without entering something...chicken and egg
JacksonHewitt: Doesn't seem to support Form 2555 either.
OnLine Taxes: I used this one in the end. I filed MFS, and it made me enter an SSN for the NRA spouse, so I entered all 9's for the SSN. (Not sure if I'll be caught out on this...) But no other issues with Forms 2555 or 8965. Note: you will need either Paypal or a US-registered debit/credit card to pay.
Hope this helps any other last minute filers out there!