I have been using Navbox Pro for VFR flight planning.
It is a good tool for the stuff one can do on a "computer" which is basically knocking up the plog. A right-click pops up airport details including (mostly accurate) contact details so you can contact them re Customs, PPR, PNR, opening hours, etc.
All "vertical" stuff i.e. altitudes to fly at, etc, has to be done by reference to the actual printed VFR charts anyway, no matter which software tool you use.
I chose Navbox back in 2002 for its good European coverage, and this remains its main asset today despite the program having hardly changed. Skydemon has a much slicker appearance but especially for those who fly beyond the UK it needs more development.
From Navbox, I print off the plog (outbound and return flight) and I print off the whole route on one page. Very quick.
For notams (a narrow route briefing) I use the NATS site. For airport-only notams (which is what one generally does on high altitude IFR flights) there are various sites e.g. avbrief.com.
I also use Avbrief for weather although nowadays there are many weather sources. Most of them get the stuff from the same source (the U.S. run GFS weather model). A lot of handy weather links are
here.
Nobody I know who flies for real uses the old circular slide rule - it's just silly.