Here is a list of prices for AD&D D&D modules sold on Ebay during last months.
Most of them (90%) are classic auctions. The majority are from US sellers, other come from Europa (essentially UK, France, Germany, Switzerland).
I've converted all European prices from Euros to US Dollars at an actual rate of 1 € = $ 1.33. UK prices have been converted at the rate of £ 1 = $ 1.48.
As everyone can see, prices are very variable : question of chance of course. The country where it's sold seems to have an importance also, as many sellers prefer to sell only in their country. Generally (in most of cases for common items), auctions end much higher when item is shipped worldwide.
The list do not pretend to be complete at all, it's just an image of the actual prices for SW items (in mint to NM condition), based on items I've "seen" during my personal searches from roughly November 2009 until now (March 2010).
Like mentioned in a earlier post, some recent auctions ended largely over $100. Most of them were bought by an Australian bidder who placed a high bid at the beginning and won each time at the end. Many bidders tried their chance during the course of the bid, then the prices increased higher than usual, even for uncommon modules.
It explains probably, as some Acaeum members confirmed here, that recent BIN auctions have been set over than $150 for uncommon items like rarest DL modules.
Hope this list could be useful for both buyers and sellers.

in US dollars, SW items in Mint or NM condition :

A1-4        126
A3        23.5
A4        14
AC1        18
AC2        19 - 16
AC3        21 - 17
AC4  38
AC6        21 - 21 -  22 - 60
AC7        30
AC10         90 - 159
B1-9        204
B2        30
B3        30
B4        30
B7        30 - 44
Book of Lairs 2         32.5
BSOLO  32.5
C6        20
WGR6  35
CA1        21 -  19
CA2        18
CM1        31
CM5  59
CM6        18.5
CM7        21 - 45
CM8        38
FRS1        20
DA2        22 - 20 - 41
DA4        26
DL1        86
DL3    28 - 86
DL12          28 - 50
DL13          13.5
DL14          35
DL15          185
DL5          16
DL9          40 -- 60 - 25
DM D Kit        27
DQ1        24.5 - 22.5 - 13.5
GAZ6  39
FR campaign set first  35
FR1        38
FR2        53 - 15
FR3        22.5 -- 25 - 34
FR6        25
FR10        24
FRE1        15
FRE2        15
FRE3        12.50
FROA1        15
GAZ10        38
GAZ12        28
GAZ13        33
GAZ4        31 - 29
GAZ8        52
H2        108.5
H4        77
I1        20
I12        168.5
I14        40 - 52 - 32
I8        30
I9        54
IM2        20
IM3        31
M1 Maelstrom        30 - 30
M2 Alphaks        20 - 13.5
M2 Maze        47 - 56
M3        32
M4        34
M5        37 - 26
N1        20
N3        40
N4        36
O1        13.5
O2        20
OA6        15.5
OP1        112.5
OA6        24.5
RS1        66 - 59
S3        23
Set 5  93
OA7        29
U3        46
UK3        16 - 17 - 39
UK6        44
UK7        44
WG4        34
WG5         40
WG7        155.5
WG9        20
WG12 44
X10        123
X13        42 -- 45 - 70
X2        13.5
X4        24.5
X6        35
X7        46
X8        19
Silver Anniversary        135

More input is always appreciated.

Some of the prices I got during the last year or so…

Hexagonal Mapping Booklet 40
AC2 10
AC5 100
AC7 18.05
BSOLO 17
D1 54.41
DL15 185.02
FR2 52.99
IM1 14
TM3 26.52
Silver Anniversary (limited) 200