The appeal's organiser, sociologist Jean-Marc Salmon, handed over a giant copy of a million-euro cheque to trade unions on Thursday.
Since 23 May, when it was launched, nearly 26,300 people have donated to the fund, which is to be extended to 7 June by public demand, according to Salmon.
Opinion polls last month showed a minority - four out of 10 - French people supporting the strike against the government's plan to reform the heavily indebted state-owned rail operator, the SNCF.
But left-wingers have rallied to the rail unions' support, arguing that they are defending a public service as it is opened up to competition and fighting for future employees' working conditions.
"You're strike is awakening great hope in the country," Salmon told the rail workers' rally where he presented his cheque.
Party HQ occupied
Paris railworkers post video of REM HQ occupation
Strikers occupied the REM headquarters in Paris for about 20 minutes on Friday after briefly invading the lower levels of Paris's Gare de Lyon station.
On the second day of the seventh block of two-day strikes, about 17 percent of employees took part in the industrial action, according to management, down slightly on the previous day.
Unions hope to give the campaign a boost on 14 May by declaring a "day without rail workers", which they hope will paralyse the network.
The reform has already passed through the lower house of parliament.
A brief occupation of the prestigious Ecole Normale Supérieure university ended on Friday when protesters against the government's plan to tighten selection for higher education left voluntarily.
Police on Thursday evacuated a buliding at Strasbourg University, leaving three other establishments occupied.
With a "Macron party" planned for Saturday, and the government beefing up police presence in case of a repeat of the violence seen on this week's May Day march, left-wingers and unions have agreed to call for a larger protest on Saturday 26 May.
They are hoping for a "people's tidal wave" that brings together strikers in various sectors and other opponents of the Macron government's policies.