I know rankings of departments are always imprecise, but I think  BU Economics should be proud that REPEC, (REsearch Papers in EConomics), which measures research output on 31 dimensions and takes an average, currently puts us at #10 in the US, just behind Yale, and ahead of Penn, Brown, Michigan and Northwestern. Keep up the great productivity!

Here is the link.
http://ideas.repec.org/top/top.usecondept.html

In case it changes before you look, or your don't have time, here are the top 30 places.

Top 25% US Economics Departments
Please note that rankings can depend on the number of registered authors in the respective institutions. Register at the RePEc Author Service.
Rank	Institution	Score	Authors	Author shares
1	Department of Economics, Harvard University Cambridge, Massachusetts (USA)
	1.02	64	50.86
2	Economics Department, Massachusetts Institute of Technology (MIT)Cambridge, Massachusetts (USA)
	2.3	41	32.55
3	Department of Economics, University of Chicago Chicago, Illinois (USA)
	3.41	41	34.28
4	Department of Economics, Princeton University Princeton, New Jersey (USA)
	3.87	47	33.41
5	Department of Economics, University of California-Berkeley Berkeley, California (USA)
	4.16	45	34.66
6	Department of Economics, New York University (NYU) New York City, New York (USA)
	6.39	54	40.17
7	Department of Economics, School of Arts and Sciences, Columbia University New York City, New York (USA)
	7.58	52	40.63
8	Department of Economics, Stanford University Stanford, California (USA)
	8.18	55	44.19
9	Economics Department, Yale University 
New Haven, Connecticut (USA)
	9.62	52	30.74
10	Department of Economics, Boston University Boston, Massachusetts (USA)
	11.89	52	42.41
11	Department of Economics, University of Pennsylvania Philadelphia, Pennsylvania (USA)
	12.33	38	33.32
12	Economics Department, Brown University 
Providence, Rhode Island (USA)
	12.76	41	37.31
13	Economics Department, University of Michigan 
Ann Arbor, Michigan (USA)
	12.86	68	53.1
14	Department of Economics, Northwestern University 
Evanston, Illinois (USA)
	12.93	35	30.54
15	Finance & Economics Department, Graduate School of Business, Columbia University New York City, New York (USA)
	14.36	25	20.52
16	Department of Economics, University of California-San Diego (UCSD) La Jolla, California (USA)
	16.29	42	34.57
17	Department of Economics, University of California-Los Angeles (UCLA) Los Angeles, California (USA)
	16.9	42	32.8
18	Economics Department, University of Wisconsin-Madison Madison, Wisconsin (USA)
	20.34	36	24.97
19	Department of Economics, Cornell University Ithaca, New York (USA)
	20.53	45	28.04
20	Economics Department, Dartmouth College Hanover, New Hampshire (USA)
	21.04	30	27.25
21	Department of Economics, Boston College Chestnut Hill, Massachusetts (USA)
	21.32	46	40.43
22	Economics Department, University of California-Davis Davis, California (USA)
	22.1	38	34.98
23	Department of Economics, University of Maryland College Park, Maryland (USA)
	22.76	43	35.97
24	Economics Department, Georgetown University Washington, District of Columbia (USA)
	23.21	43	34.12
25	Department of Economics, Duke University Durham, North Carolina (USA)
	23.95	43	34.71
26	Department of Economics, Vanderbilt University Nashville, Tennessee (USA)
	25.5	33	31.14
27	Department of Economics, University of Minnesota Minneapolis, Minnesota (USA)
	26.67	27	20.99
28	Economics Department, Michigan State University East Lansing, Michigan (USA)
	27.5	38	32.35
29	Economics Department, Stern School of Business, New York University (NYU) New York City, New York (USA)
	27.98	23	20.61
30	Department of Economics, University of California-Santa Barbara (UCSB) Santa Barbara, California (USA)
	29.55	31	26.08

This page shows one of the many rankings computed with RePEc data. They 
are based on data about authors who have registered with the RePEc Author Service, institutions listed on EDIRC, bibliographic data collected by RePEc, citation analysis performed by CitEc and popularity data compiled by LogEc. To find more rankings, historical data and detailed methodology, click here. Or see the ranking FAQ.
These rankings take only into account institutions registered in EDIRC and authors registered with the RePEc Author Service
 and the institutions they claimed to be affiliated with. For US 
Economics Departments, these are 478 institutions. Institutions need 
satisfy the following criteria to be included: Institutions having the 
following words in its name or its name translation on EDIRC: Economics and one of School, Department, Division or Faculty; be located in the United States.