23-year-old striker Guy Madjo joins the Red Devils from rivals Forest Green Rovers, while 25-year-old midfielder Tyrone Thompson signs on as a free agent after his contract with Halifax Town expired at the end of the season.
20-year-old striker Jon-Paul Pittman played for Doncaster last term but was released at the end of their campaign.
He becomes the seventh new face to arrive at Broadfield Stadium and manager Steve Evans is expected to make some more acquisitions in the coming weeks.
"Tyrone is someone I worked with as a youngster at Sheffield United and have continued to watch his career since leaving United," Reds' assistant manager Paul Raynor told the club's official website.
"He was fantastic for Halifax last season, hence the strong interest for his signature.
"In fact we tried to sign the boy at Boston United, but unfortunately for the Gaffer and myself, it was in the period when we had to sell players and we were embargoed from bringing any players in.
"As for Guy Madjo, he is an outstanding talent with frightening pace who has a real eye for a goal. In simple terms, he will be a tremendous signing, excite our supporters, and he was a primary target for the Gaffer and myself when we took the job here at Crawley Town.
"The lad had numerous clubs after his signature and quite rightly he has taken his time to make sure he joins the right club at the right time. It is a nice bonus for us considering the work the Gaffer has put into this over the last few weeks and when you also consider he could have been much more financially rewarded had he gone else where
"He also brings competition for the likes of Magno Vieira, J-P Pittman, and with the Gaffer locked in talks we could possibly have another two strikers on-board by early next week.
"Competition for places through out the team is getting stronger, and is sure to be fierce by the opening day of the season as I can assure our supporters we have a number of exciting trialists also joining us when the lads report back on Monday.
"We will look at those trialists with the view to signing them should they show the attributes we are looking for."
Source: http://www.confguide.com/newsArticle.do?id=6722