bests idea for a saas business
1. A social network for introverts
People are always complaining about social media. Make a social media that caters to the other half of the population: introverts. The site would look similar to Facebook but every post would be private unless you chose to make it public. You could only "friend" people who you have met in real life. The idea is that people can interact without having to deal with all the stress of public opinion and everyone can post what they want when they want (as long as its private). This solves the problem of introverts not being able 2 "network" or "meet people". They can still do all those things on this site but without any pressure.
2. A dating site for people over 50
There's a huge market here but there's no good sites for it. I've tried a few and they are horrible. People over 50 are very active online but most sites cater to much younger people.
3. An anti-Twitter
I'm not sure how this would work but I know many people who have stopped using Twitter because of too much negativity, trolls, etc. Make a site where people can post whatever they want (like Twitter) but no one else can see it unless they like it (like Instagram). This way, positive news can spread instead of negative news which often gets more attention because it's more shocking than boring positive news stories that don't get attention.
4. A lightweight CRM for small businesses
A CRM is software used by salespeople to keep track of their leads and contacts and activities related to each lead or contact. Salesforce is probably the biggest CRM out there but many businesses find it too expensive or too heavy or both so they use something else (which means less money for Salesforce). There are many lighter options out there but none as big as Salesforce so this would be an opportunity if you made a CRM that was half the price and half the weight and had all the basic functionality needed by most businesses at 80% of their customers (in other words, don't try to compete with Salesforce head on; go after their smaller customers who don't want them anymore).
5. A better version of AirBnB / HomeAway / VRBO / Couchsurfing / etc combined into one website
These are all sites where people rent out their homes while they are away temporarily or permanently. But these sites have been around forever so there's little innovation happening on them despite their high usage among travelers and homeowners alike. The reason is because these sites rely on old technologies (phone calls, emails, faxes) in order to book stays so there's no easy way for someone renting out his home to also manage his calendar, answer questions from guests, etc., So create a site that combines everything into one interface so renting your home becomes easier than ever before.