The 33-year-old made 19 appearances for the Seagulls last term after joining on loan in January, helping them finish third, before a play-off semi-final defeat by Sheffield Wednesday.
Sidwell played only four games for Premier League club Stoke last season.
"He knows exactly what the Championship is all about and what it takes to get promoted," manager Chris Hughton said.
"He was excellent for us in the run-in, and was a key figure on and off the pitch as one of the senior members of the squad."
Find all the latest football transfers on our dedicated page.Haigh, 39, left Leeds in April 2014 after Massimo Cellino bought the club.
"Penzance is a great grounding of a club, with an awful lot of potential to grow in the community," Haigh told BBC Radio Cornwall.
Penzance are bottom of the South West Peninsula League Division One West, the 11th tier of English football.
"The club contacted me through Twitter asking if I could help out," Haigh said. "I'd had one or two offers since Leeds, and I said no to them.
"But, the reason why I said yes to Penzance is because of the potential. They're at the bottom, so they can only go up.
"What I liked when I chatted to the committee was the passion. They're without debt, they can build on that and that's why I was really interested."
After leaving Leeds, Haigh moved to Dubai where he was acquitted in March over charges of sending an offensive tweet about a business partner.
But, he served a two-year sentence on separate charges of financial misappropriation.
Haigh, who grew up in Cornwall and has relocated to the county since leaving Dubai, will be sponsoring Penzance rather than financially backing them.
"There's no reason why clubs in Cornwall can't play at a higher level," he added. "But, it's going to take some investment in terms of infrastructure."He has launched a consultation to try to find agreement on how universities should be paid for.
The consultation has been called the 'Big Conversation'.
Speaking in the assembly, Mr Farry said that Northern Ireland was the only part of the UK actively "disinvesting" in higher education.
The consultation process will involve a number of events and online presentations in order to seek opinion from students, university staff, unions and the wider public.
Just under 40% of funding for Queen's University, Belfast (QUB) and Ulster University comes directly from Stormont's Department for Employment and Learning (DEL).
However, the universities faced cuts of more than £16m in funding from DEL in 2015/16, which followed cuts in funding during previous years.
Ulster University is shedding about 200 jobs in 2015/16 and 1,200 student places over the next three years, while Queen's University announced in April that it was cutting 236 jobs in 2015/16 and 1,010 student places over the next three years.
Ulster University also closed a number of courses and departments including their School of Modern Languages at Coleraine, County Londonderry.
The universities also draw about 30% of their annual funding from student tuition fees, which are currently £3,805 per year for students from Northern Ireland.
Some students also study for degrees at further education colleges, and that budget was also reduced this year by about £12m.
DEL's budget was reduced by £62m earlier this year, and its budget for higher education institutions fell from £203m to £186m, a reduction of 8.2%.
Mr Farry said that, given its importance to the local economy and the fact that just under half of young people in Northern Ireland entered higher education, the status quo was no longer an option.
During subsequent questions, a number of MLAs including Phil Flanagan of Sinn Féin, Jim Allister of the Tradition Unionist Voice (TUV) and Basil McCrea of NI21, expressed concern about a possible rise in tuition fees.
In response, Mr Farry said that he had an "open mind" and that "this is not a conversation about whether we have fees or don't have fees".
"All options have to be on the table and fees are only one of many options facing us. This is not a done deal process."
The consultation ends on 23 October, and Mr Farry said he wanted to present options to the Northern Ireland Executive in the autumn.Russell Sherwood, 69, of Cilfrew, Neath, went missing while heading to Ewenny, Vale of Glamorgan, after Storm Angus hit in November.
Three days later, his body was found in the River Ogmore.
The Independent Police Complaints Commission (IP