Here are holidays and sporting events for 2009 amd 2010. Note that the 3 day weekends can get very crowded as well as sporting events. We recently expanded the 2010 holiday listings.
2009
Month
Day
Weekday
Long Weekend
Busy?
Martin Luther
Jan
19
Monday
For Some
Yes
Chinese New Year's
Jan
26
Monday
No
No
Superbowl XLIII
Feb
1
Sunday
No
200,000+
Valentine's
Feb
14
Saturday
No
Yes
President's Day
Feb
16
Monday
Yes
Yes
Nascar
Feb
27
Friday
No
100,000+
St. Patrick's
Mar
17
Tuesday
No
Average
March Madness
Mar
19
Thursday
No
200,000+
Final 4
Apr
4
Saturday
No
No
Cinco De Mayo
May
5
Tuesday
No
No
Memorial Day
May
25
Monday
Yes
Yes
July 4th
July
4
Saturday
No
Yes
Labor Day
Sep
7
Monday
Yes
200,000
Columbus Day
Oct
12
Monday
Yes
Yes
Halloween
Oct
31
Saturday
No
Yes
Veteran's Day
Nov
12
Monday
Yes
Yes
Thanksgiving
Nov
26
Thursday
Usually
No
Christmas
Dec
25
Friday
Yes
No
New Year's Eve
Dec
31
Thursday
Yes
200,000
Here are the expanded holidays for 2010. Note that although Purim is not as major a holiday it is a better fit for Vegas.