Average Donation
In the first quarter, Clinton's donation average was up at $370, Edwards was at $350, and Obama's at $246.  Based on the current numbers, he would have an average donation of around $211.  For comparison, on the Republican side their donation averages have been around double Obama's: Mitt Romney had an average donation in the first quarter of $646, Giuliani of $519, and it seems that Mitt Romney needed an infusion of personal funds to reach the $20 million mark again this quarter after facing a drop-off in donations.  (It's interesting that Edwards looks like he is facing a pretty dramatic drop-off in his average donation, from $350 in the first quarter to $150 in the second.  Big donors backing away from the campaign?)

Why Does this Matter?
Aside from all of the reasons to be excited about having 258,000 donors individually contributing to the campaign as a sign of enthusiasm for the campaign, there's also an ever-widening financial gap among the candidates.  Jerome points out, Kerry needed only $5 million in the last three months to win the 2004 Iowa caucus, but we're starting to see a much more dramatic funding divide.  Obama will have raised a total of $56 million, Clinton around $38-40 million (plus $10 million from the Senate campaign fund), Edwards around $23 million, Richardson around $13-14 million...  Biden and Dodd will probably be lucky to break into the double-digits.  And this gap will probably only continue to widen between the tiers.  
There's a really good question here.  Do funds help that much in Iowa?  Or will they make Iowa irrelevant --- as the candidates picking up momentum there will be unable to compete with the sheer amount of money spread out across a national primary on Feb 5th?  Will candidates like Clinton and Obama actually reach the heights of $80-100 million before the primaries even start?  It seems almost certain at this point.  These are figures we simply aren't used to seeing until the general election.  
And will the gap between Clinton and Obama potentially continue to grow as Obama relies on a massive list of small-donor repeat-givers and Clinton continues to exhaust her big donors giving up to the limit?  74% of Clinton's first quarter total came from donors giving $2,300 or more, in contrast with 49% for Obama and 47% for Edwards.  (Obama is still showing serious growth in the second quarter and Clinton basically matched her first quarter numbers, all the other Democrats seem to have dropped off and remained steady.)

A Different Kind of Campaign: The "Enthusiasm Gap"
What Obama's campaign has really shown is the extraordinary success of his strategy of calling on ordinary people to own a piece of his campaign.  His large donor base has also shown extraordinary loyalty, since his 258,000 donors donated an average of almost 1.4 times.  The numbers (104,000 donors in first quarter, 100,000 more contributions than donors in the second) suggest that a lot of his first quarter donors came back in the second.  This suggests a loyal and dedicated base --- they are donors that continue to come back and give.

Comparisons with Dean
Although it's accurate that the 2008 campaign heated up more quickly than in 2003, it is still extraordinary that the Obama campaign's 258,000 in the first six months rivals Dean's 280,000 for the entire year of 2003.  The number also rivals the size, according to some commentators (I have yet to see the stats), of the Clintons' famous rolodex from their years in the White House.  

Is Obama setting himself up to be the next Dean?
Obama's campaign has shown itself to be keen on learning from the lessons of the Dean campaign.  Depending on who you ask, you will get fifty different explanations for what went wrong, but just to focus on a couple of the big ones, I think Dean's defeat is not comparable for a number of reasons --- one of the best is that he ran into the wall of an anti-Dean vote who saw him as too liberal for the general election.  The Iowa caucus requires supporters of candidates under 15% who pick another candidate, allowing the system to deflate the results of the insurgent candidate.  Second, Dean very quickly ran out of funds to make a comeback.  Third, in 2003 Democrats were in a hurry to pick a challenger to an incumbent president.  In this case, the Republican primary looks to me as if it might even last longer and be more competitive than the Democratic one.
Why is Obama better positioned?  
First of all, his base of volunteers isn't on the blue coasts but in Illinois, a neighboring state, where they have already started a "Sister Cities" program to match volunteers with communities in Iowa and continue to send them back again and again to get to know the community instead of showing up the weekend before the election.
Second, both Obama's running behind in the national polls and Dean's defeat are going to keep the campaign grounded.  The campaign knows it has a serious fight.  This might just help it keep focused on building its organization in the early states.  Camp Obama, about which many have posted, is churning out interns to fan out to the early states and with a good head-start over previous election cycles.
In short, Obama is doing everything right.  He's building his campaign, training volunteers, encouraging small donors to own a part of the campaign, building connections through its social networking site, raising funds, etc.  It's important to focus on how extraordinary his accomplishments have been so far.  If there wasn't another candidate named Clinton in this race, Obama would undoubtably be the clear front-runner, which is an amazing accomplishment for an African-American candidate.

Anyway, those are some thoughts...

Sources for First Quarter Stats:
http://www.opensecrets.org/pres08/index. asp?cycle=2008
http://projects.washingtonpost.com/2008- presidential-candidates/finance/2007/q1/