It seems that the two most popular logging software programs are N1MM Logger+ and N3FJP Logger. Both operate only on Microsoft Windows, so if you're using Linux you either need to use Wine or a different logging program.
I've used N1MM for contest logging for a long time, but I feel I've only scratched the surface of its capabilities. It has hundreds of features designed to shave fractions of a second from the contest exchange and logging process. Calling it a logger is an understatement, as it can also control and operate the radio by sending CW or recorded voice messages. It also knows how to interoperate with WSJT-X or JTDX for use with FT8/FT4 and other modes.
N3FJP is also very popular. It is simpler than N1MM+ and has fewer features, although its capabilities have been increasing steadily. Most of our operators on Field Day use it. It costs around $10-20 for a perpetual licence including updates.
Let me give an example of shaving fractions of seconds from the exchange. The CW in N1MM+ messaging facility will send CQ for you, as well as the contest exchange (e.g. "5A GTA" that the club station uses on field day) and the final thank you at the end of the exchange as well as messages like "AGN?" which can be useful from time to time. The CW can be tailored to speed up when there's something that is totally expected by the other station, like his own call sign, then slow down again when the exchange information is sent. Another example is that the spacing between CW characters can be changed from the standard 7 dits to 6 dits. That might reduce the message time by 50ms or so, which might add up to 5 or 10 more contacts over a 24 hour contest.
Learning N1MM+ can be daunting, but well worth the the time invested. The first time I used it I had it set up for RTTY in a hour or so. Support by N1MM himself and the team is excellent on the Google group and the program is free-of-charge (but not open source). I don't use N1MM+ for my general logging but after the contest I can produce an ADIF format file for upload to my regular logger which I then use to confirm the contacts in ARRL Logbook of the World.
It is truly an amazing and comprehensive tool to make your contest experience fun and productive. Here's a link to a video by the RATPAC team (who have lots of great videos) on using N1MM+ on ARRL Field Day.
Topic: N1MM Logger for Field Day
Speaker/Presenter: Anthony Luscre, K8ZT
View Video: https://vimeo.com/561658305
Download Video: https://vimeo.com/user107547861/download/561658305/d3de10fd9e