Answers!
1. Result of the Roman census for 147/46 BC.322,000. By 147/46 BC the Roman Republic was in its golden years, with territorial expansion having just begun to acquire continental scale and extension of citizenship to far-flung provinces still a few decades into the future.
250,000 - Chulk77,777 - Friker
15,000 - Akoss Poo
666,666 - CTG
2,980,400 - Usrin
4,500,000 - Alan Rotoi
7,500,000 - Bonzai Joe
21,000,000 - Zak McKracken
2. Typical (measured for just one specimen) migration distance for an Amur Falcon, in km (just one leg of the route only).
14,560km.
12,000 - Alan Rotoi11,000 - Zak McKracken
6,666 - CTG
5,700 - Akoss Poo
4,500 - Usrin
4,400 - Bonzai Joe
3,777 - Friker
3,000 - Chulk
3. Fuel consumption of a Lotus Elan Sprint (the 1970-73 model), in km/L.
8.5km/l. This beauty has a four cylinder 1558cc engine.
7.15 - Zak McKracken7 - Friker (ouch!)
4.5 - Bonzai Joe
4.22 - Akoss Poo
13 - Chulk
4 - Usrin
15 - CTG (that is 6.666l/100km, in case you are wondering.)
41.7 - Alan Rotoi (submitted as 2.4l/100km.)
4. 2012 third quarter cellphone sales in Brazil, in number of phones.15,300,000.
19,000,000 - Zak McKracken20,000,000 - Chulk
10,000,001 - CTG
8,050,000 - Usrin
5,200,001 - Akoss Poo
3,146,611 - Bonzai Joe
2,358,431 - Alan Rotoi
77,777 - Friker
5. London Underground average speed, including stops at stations, in km/h.33km/h.
33 - Zak McKracken (!)
30.5 - Usrin
37 - Friker
38 - Akoss Poo
40 - Chulk
42 - Bonzai Joe
23 - CTG
60 - Alan Rotoi
6. Area of the Congo River basin, in km2.3,700,000km2.
2,500,000 - Chulk2,100,000 - Usrin / Akoss Poo
6,666,666 - CTG
340,000 - Zak McKracken
49,000 - Bonzai Joe
750 - Alan Rotoi
77 - Friker
7. Total number of second places in F1 races between Coulthard, Barrichello and Webber as of today.66.
66 - CTG (LOL!

)
77 - Chulk (not Friker)
43 - Akoss Poo
99 - Usrin
24 - Bonzai Joe
21 - Zak McKracken
17 - Friker
14 - Alan Rotoi
8. Lines of source code of DOSBox as of today.119,251. "As of today" referred, rather confusingly, to the day the questions were posted. In any case, it seems that there were no commits to the DOSBox repository over the last two weeks.
96,000 - Zak McKracken
16,000 - Akoss Poo
10,777 - Friker
7,000 - Alan Rotoi
2,348 - Usrin
779 - Bonzai Joe
500,001 - Chulk
666,666 - CTG
9. Length of the free-form improvisation section at the end of King Crimson's Moonchild.9min42s. The rest of the song is 2min30s long, by the way.
7min31s - Bonzai Joe6min30s - Zak McKracken
3min57s - Friker
2min24s - Akoss Poo
1min57s - Usrin
1min37s - Chulk
1min06.6s - CTG
30min - Alan Rotoi
10. Distance between western and eastern extreme points of São Paulo, Brazil (the city, not the state).48.3km. Note that a quick glance at a city map
like this one can be slightly misleading, as the westernmost point is on the northwestern "horn".
55 - Zak McKracken59 - Bonzai Joe
35 - Chulk
64.8 - Usrin
31 - Alan Rotoi
72.1 - Akoss Poo
101 - CTG
277 - Friker
11. Number of numbered sections/aphorisms in Friedrich Nietzsche's Beyond Good and Evil.296.
277 - Friker350 - Chulk
239 - Akoss Poo
214 - Bonzai Joe
146 - Alan Rotoi
123 - Zak McKracken
666 - Usrin
6,666 - CTG
12. Estimated total population of Asian Elephants (quoted from a 2011 paper).43,445. Endangered, though not critically so.
50,000 - Chulk24,800 - Zak McKracken
6,666 - CTG
1,240 - Bonzai Joe
1,200 - Akoss Poo
400 - Alan Rotoi
77 - Friker
974,000 - Usrin
13. Average number of “componentes” (i.e. people in costumes dancing or playing instruments) per samba school (main group only) at the Rio de Janeiro carnival parade in 2009.4264. Times twelve schools, that gives about 51,000 people parading during two nights.
1500 - Chulk577 - Friker
345 - Zak McKracken
66 - CTG
52 - Usrin
40 - Alan Rotoi
23.5 - Akoss Poo
18 - Bonzai Joe
+1. Time difference between the longest and shortest final laps sent by me to a Stunts competition (LeStunts races excluded).Longest: 3:59.65 (Round 11 of WMCS 2009/10)
Shortest: 0:31.10 (Paks, USC 2007/08)
3:29.55.
2:59.00 - CTG4:18.00 - Usrin
2:05.00 - Zak McKracken
1:39.00 - Bonzai Joe
1:37.00 - Friker
1:08.75 - Akoss Poo
1:07.00 - Chulk
0:56.00 - Alan Rotoi
Results of round 115 - Zak McKracken (two in a row!)
4 - Chulk (still in strong form...)
2 - CTG
1 - Friker / Alan Rotoi / Bonzai Joe
0 - Usrin / Akoss Poo
Overall standings36 - Chulk
27 - Zak McKracken
22 - Duplode
21 - Akoss Poo
20 - Usrin
17 - Bonzai Joe
8 - CTG
4 – Friker
3 - Argammon
2 - SuperBrian
1 - Alan Rotoi
(Note that this overall chart doesn't make much sense now that the winner gets no points from the following round.)
Thanks for joining, this was good fun
Edit: Swapping Akoss' and Usrin's answer to #12; it did not change the results.